Understanding Stoichiometry: Key Concepts and Calculations
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Mindanao State University - Iligan Institute of Technology**We aren't endorsed by this school
Course
CHEM 12
Subject
Chemistry
Date
Dec 11, 2024
Pages
59
Uploaded by ChiefIce15679
STOICHIOMETRY●The relationship between thequantities of reactants andproducts before, during, andfollowing chemical reactions●All reaction stoichiometryrelationships start with abalancedchemical equation.●Equation gives therelativenumbers of molesof reactantsand products.●Problems are solved usingratiosfrom the balanced equation.Greek words of Stoichiometry:StoicheionmeanselementMetronmeansmeasure●Stoichiometry is about measuringthe amounts of elements &compounds involved in reaction.●If the amounts of the separatereactants are known, then theamount of the product can becalculated.●Conversely, if 1 reactant has aknown quantity and the quantity ofthe products can be empiricallydetermined, then the amount of theother reactants can also becalculated.4NH3+ 5O26H2O + 4NORecall that Chemical formulas arebalanced with coefficients4 x NH3= 4 nitrogen + 12hydrogen5 x O2= 10 oxygen6 x H2O= 12 hydrogen + 6oxygen4 x NO= 4 nitrogen + 4 oxygenStoichiometric CalculationsThe coefficients in the balanced equationgive the ratio of moles of reactants andproducts4NH3+5O26H2O +4NOWith Stoichiometry we find out thatCoefficients like4 : 5 : 6 : 4convey the ratio of substances needed fora reaction to occur, in terms of moles(mole ratio)4 : 5 : 6 : 44 moleculesof NH3 react with5moleculesof O2 to produce6 moleculesof H2O and4 moleculesof NOOR4 molesof NH3 react with5 molesof O2to produce6 molesof H2O and4 molesof NO
Stoichiometric CalculationsFrom the mass of Substance A, we canuse the ratio of the coefficients of A and BtocalculatethemassofSubstance Bformed (if it’s a product) or used (if it’s areactant)1.MOLE-MOLE RELATIONSHIP●Given and unknownquantities are in molesAmount of Given→Amount of UnknownSubstance (mol) Substance (mol)Example:Ammonia(NH3) can be formedby the reaction between nitrogen gas (N2)and hydrogen gas (H2).How manymoles of H2are required toproduce5.0 moles NH3?1 mol N2requires3 mol H2to give2 mol NH3Thus, mole ratio (conversion factor):3 mol H2: 2 mol NH32.MOLE-MASS RELATIONSHIP●Given quantity is amount inmoles and unknownquantity is amount in gramsAmount of given→Amount of unknownSubstance(mol) Substance(grams)HowmanygramsofMgOcanbeproduced from 10.0 moles of O2used?given: O2= 10 molesReq’d: mass of MgO3.MASS-MASS RELATIONSHIP●Given and unknownquantities are amounts ingramsAmount of given→Amount of unknownSubstance(grams) substance(grams)
How many grams of water can be formedif the amount of H2used is 50.0g?Given: H2=50.0gReq’d: mass of H2OMR: 2 mol H2:2 mol H2O4.VOLUME-VOLUMERELATIONSHIP●Given and unknownquantities are in terms ofvolumeAmount of given→Amount of unknownSubstance (liter) substance(liter)What volume of hydrogen gas (H2) willreact with 25.0L of nitrogen gas (N2) toform ammonia gas (NH3) at StandardTemperature and Pressure (STP)?Given: At STP, T = 273 K (0oC)P = 1 atmvolume of N2= 25.0 L5.MOLE-VOLUME RELATIONSHIPCalculate the volume of H2produced at STP if 0.5 mol of sodiumreacts with water?6.MASS-VOLUME RELATIONSHIPHow many liters of Sulfur dioxide gas(SO2) at STP are formed when 25.0 gramsof Sulfur burns?
Limiting Reagent& Percent YieldLimiting Reactant or Limiting Reagent●The reactant present in thesmalleststoichiometricamount.●The reagent or reactant that limitsthe amount of product that can beformed and is completelyconsumed when the reaction iscomplete.Excess Reactant●The reactant that remains or notfully consumed once the reactionhas stopped due to the limitingreactant being exhausted already.Theoretical Yield●The amount of product that can bepossibly produced fromstoichiometry or “perfect” reaction.Actual Yield●The amount actually produced andmeasured.●Actual yield amount is oftentimeslower than the theoretical yield.Percent Yield●Comparison of the amountbetween what’s actually obtainedand the amount it was possible toproduce.Limiting Reactants Method 11.Write a balanced equation.2.For each reactant, calculatestoichiometrically the amount ofproduct formed either in terms ofmoles or mass in grams.3.Smaller value indicates:
●limiting reactant or limiting reagentLimiting Reactant Method 21.Begin by writing a correctlybalanced chemical equation2.Write down all quantitative valuesunder equation (include units)3.ConvertALLreactants to moleunits4.Divide by the coefficient of eachreactant5.The smallest value obtained is thelimiting reactant.Example 1 :●Consider the equation of roastingLead(II) sulfide (PbS) in oxygen(O2) to produce Lead(II) oxide(PbO) and Sulfur dioxide(SO2).●Which do you think is the limitingreagent?●Which reactant is in excessamount?2PbS +3O2→2PbO +2SOIn reality, theactual yieldis not the sameas the stoichiometrically●Calculated theoretical yield.Percent yield, then, is expressed in thefollowing equation:Theoretical YieldIf 170 g of Lead (II) oxide is obtained, thenthe % yield would be calculated as follows:Example 2:CH4+ 2O2→ CO2+ 2H2O25.0 g of CH 4 is chemically reactedwith 25.0 g O21. Which is the limiting reagent? Excessreagent?2. Calculate the mass in grams of CO2that could be produced.3. What mass of the excess reagent wasreacted or consumed?4. Calculate the mass in grams of theexcess reagent that will remain unusedafter the reaction.5. If 12.5 g CO2 is obtained, calculate the% yield.
The Gas Laws●What are gases?●How do we define a gas?●What are physical properties ofgases?●How are gases different fromliquids and solids?Gas Behavior●Gases do not have a definitevolume or shape like liquids orsolids.●They also behave according to thesurrounding physical conditions,which is different than liquids orsolids.So how can we predict how gases willbehave in certain situations?Kinetic Molecular Theory●The kinetic molecular theory (KMT)is based on the idea that particlesof matter are always in motion.●This theory can be used to helpexplain the properties of gases…along with solids and liquids.●We can use the KMT to explain thebehaviourofgasesandtheirphysical properties.●KMT assumes an ideal gas, a gasthat fits all the assumptions of thetheory. The KMT is based on fivedifferent assumptions.Assumption 1●Gases consist of large numbers oftinyparticlesthatarefarapartrelative to their size●Thusgaseshaveverylowdensitiescomparedtosolidsorliquids●Gas molecules are treated as pointparticles that move randomly at awide range of speeds.●Densityisthecriticalfeaturedistinguishing a gas from liquid andsolid,wheremoleculesaresotightlypackedthattheyareconstantly in contact.●Unlikesolidand liquid, gas canexpand or contract easily.●The average distance between gasmolecules is about 10 times thediameterofthemoleculesthemselves.Compressed gases are used in manysituations.●In hospitals, oxygen is often usedforpatientswhohavedamagedlungs to help them breathe better.●Ifapatientishavingamajoroperation,theanesthesiaadministered is a compressed gas.●Welding requires very hot flamesproduced by compresses
acetylene and oxygen mixtures.●Many summer barbeque grills arefueled by compressed propane.Assumption 2●Collisionsbetweengasparticlesandbetweenparticlesandthecontainerwallsareelasticcollisions●Elastic collisions are where there isno net loss of kinetic energy.Assumption 3●Gas particles are in constant,rapid, random motion.●They therefore posses kineticenergy, which is energy of motion.●Molecules move in a straight lineunobstructed until it collides withanother molecule or strike the wall.Assumption 4●There are no forces of attraction orrepulsion between gas particles.●Think of ideal gases as pool balls;when they collide, they do not sticktogether but bounce apart.●Themoleculesexertnoelectrostaticforcesamongstthemselves nor with the walls ofthe container.Assumption 5●The average KE of gas particles isproportionaltotheabsolutetemperature.●All gases at the same temperaturewill have the same KE.
●The average KE of the moleculesis directly proportional to theabsolute temperature.m=mass v=velocityke=kinetic energyroot mean square (rms) speed (vrms)Amonton’s Law●ThePexerted by a gas is directlyproportional to theTas long as theVis constant. The average KE of agas molecule depends only on thetemperature of the gas. Thus, theaverage KE of the gas particlesincreasesasthegasbecomeswarmer.●An increase in average KE meansan increase in average molecularvelocity.Thefastertheseparticlesmovejustbeforehitting the wall, the greater theforcethey exert on the wall.Sincetheforcepercollisionincreases as theTrises and theVremains constant, thePof the gasmust increase as well.So, why does the KMT matter?We can use the KMT to account for thephysical properties of gases.●helium●air●water vaporPhysical Properties of Gases●Gases will expand to completely fillany enclosed container.●Gases therefore do not have adefinite shape.Compressibility●Gases are compressible●Gas molecules can be crowdedclose together
The volume occupied by a gas can bereduced because gas molecules canmove closer together.●Gases will also effuse anddiffuse> Diffusionis when differentgases mix together> Effusionis when gases escapethrough a small openingWhat is pressure?●Pressure is the amount of force perunit of surface area●The SI unit of measure of force isthe newton, N●A barometer is used to measurepressure●The pressure depends on thenumber of times per second thatthe molecules strike the walls ofthe container.●If the gas is compressed to asmaller volume, the same numberof molecules is now acting againsta smaller surface area. As a result,the number striking per unit area,or the pressure, is now higher.Units of Pressure●Although aNewton (N)is the SIunit for force, in this class we aregoing to use other units.●mmHg:millimeters of mercury.The average atmospheric pressureat sea level and 0°C is760 mmHg.●atm:One atmosphere is exactlyequivalent to760 mmHg.●Pa(Pascal): the pressure exertedby a force of1 newton●(N)acting on an area of onesquare meter.●PSI: pound per square inchConversions between units ofPressure●1.00 atm = 760 mmHg●1.00 atm = 1.01 x 105Pa●1.00 atm = 101.3 kPa (kilopascal)●1.00 atm = 760 torr (to honorTorricelli for inventing thebarometer. Not used as often.)
●1.00 atm= 14.7 psi (pounds persquare inch)●Convert 3.6 x 102atm to torr> 270,000 torr●Convert 859 torr to atm> 1.13 atm●Convert 5.0 x 109Pa to atm> 4.9 x 104atm●Convert 263 kPa to Pa> 2.63 x 105Pa●Convert 7.83 atm to mmHg●Convert 5.95 x 103mmHg topsiSTANDARD TEMPERATURE ANDPRESSURE●For purposes of comparison,scientists have agreed on standardconditions of exactly 1.00 atmpressure and 0°C.●WHY??●These conditions are calledStandard Temperature andPressure●Remember: STP means 1.00 atmof pressure and 0°C.Gas Laws●Gas laws are simple mathematicalrelationships between volume,temperature, pressure and quantityof a gas.●These variables can be changedand the results can be observed.LEAPINGRUBBERexplosively createdfrom butadiene gas in bottle is discoveryof MIT's Dr. A. Morton, that exemplifies thekind of chemical magic which Monsantoand others put to commercial use.Real Life Application●How do hot air balloons work?●What do they change to get off theground?●Does this relate to gases?●Relates pressure and volume●What can be interpreted from thisgraph about volume and pressure?This pressure-volume graph shows aninverserelationship:aspressureincreases, volume decreases.
●Boyle’s law states that the volumeof a fixed mass of gas variesinversely with the pressure at aconstant temperature●Mathematically, his law isexpressed as●Where V is volume, P is pressureand k is a constant●Boyle’s law can be used tocompare changing conditions for agas●Where P1and V1are initialconditions and P2and V2are newconditions.ExampleA sample of oxygen gas has a volume of150. mL when its pressure is 0.947 atm.What will the volume of the gas be at apressure of 0.987 atm if the temperatureremains constant?The final volume would be 144 mL of O2Each day, hundreds of weather balloonsare launched. Made of a synthetic rubberand carrying a box of instruments, thehelium-filled balloon rises up into the sky.As it gains altitude, atmospheric pressurebecomes less and the balloon expands.At some point the balloon bursts due tothe expansion, the instruments drop(aided by a parachute) to be retrieved andstudied for information about the weather.●Relates volume and temperature●What can be interpreted from thisgraph about volume andtemperature?The graph shows a direct proportionalitybetween the volume of a sample of gasand the temperature.
THE GAS LAW BEHIND HOT AIRBALLOONSCharles’ Law●Charles’slawstatesthatthevolume of a fixed mass of a gas atconstantpressurevariesdirectlywiththetemperatureinKelvinscale.●Mathematically,hislawisexpressed as Where V is volume,Tistemperatureandkisaconstant●Charles’s law can applied directlytomostvolumetemperatureproblems involving gases by thisequation.●WhereT1andV1areinitialconditions and T2 and V2 are newconditions●Everybodyenjoysthe smell andtaste of freshly-baked bread. It islight and fluffy as a result of theactionofyeastonsugar. Yeastconverts the sugar to CO2, whichat high temperatures causes thedoughtoexpandandbecomelighter.Theend-resultisanenjoyabletreat,especiallywhencovered with melted butter●A inflated balloon inside a warmbuildingwillshrinkwhenitiscarried to colder area●Human lungs’ capacity is reducedincolderweather.Runnersandother athletes may find it harder toperform in cold weather●Carenginesduringcombustionworks by this principle. The heatfromthecombustion of the fuelcausesthecylindertoexpand,which pushes the piston and turnsthe crankshaft.●ACokecanwithheatedsmallamount of water near its boilingpointisimmediatelyinvertedintice-cold water making the cokecan experience a drastic drop in T.Thecan’s vol will decrease causingthe can crush in on itself.GAY-LUSSAC’S LAW●Relates pressure andtemperature
●What can be interpretedfrom this graph aboutpressure and temperature?❖GRAPH:-GaspressureisdirectlyproportionaltoKelvintemperatureatconstantvolume●Gay-Lussac’s law states that thepressure of fixed mass of gas atconstantvolumevariesdirectlywith theKelvin temperature.●Mathematically,hislawisexpressed as❖Where P is Pressure, T istemperature and k is aconstant●Gay-Lussac’s law can be used tocalculateunknownvaluesusingthe following form❖Where P1and T1are initialconditions and P2and T2are new conditionsEXAMPLES:●The gas in an aerosol can is at apressureof3.0atmat25°C.Directionsonthecanwarntheuser not to keep the can in a placewherethetemperatureexceeds52°C.Whatwouldthegaspressure be in the can at 52°C?●The final pressure would be in 3.27atm.COMBINED GAS LAW●Agassampleoftenundergoeschanges in temperature, pressureand volume at the same time. Agassampleoftenundergoeschanges in temperature, pressureand volume at the same time.●Whenthishappens,Boyle’s,Charles’sandGay-Lussaclawsmust be combined●The combined gas law expressesthe relationship between pressure,volume and temperature of a fixedamount of gas
●Mathematically, this is expressedas●Where P is pressure, V is volume,Tistemperatureandkisaconstant●Thecombinedgaslawcanbeusedtocalculatedifferentconditions for equal quantities ofgases●Thecombinedgaslawcanbere-written as follows●Where P1, V1, and T1are initialconditions and P2, V2, and T2arenew conditionsEXAMPLE:●A helium filled balloon has avolume of 50.0 L at 25 °C and 1.08atm. What volume will it have at0.855 atm and 10°C?●The final volume will be 60.0L ofHelium.COMBINED GAS LAW APPLICATION●In everyday life, the combined gaslaw has several applications. Whenthe amount of gas remainsconstant, but the pressure, volume,and temperature fluctuate, this ruleapplies. Cloud formation, fridge,and air conditioners are predictedby this law.●In scuba divers, human lungs arethe container that holds the gas.The pressure in water is greaterthan pressure in air, and waterpressureincreaseswithdepth.Witheachadditionalfootthatdiversdescend,waterpressurerises.Thus,diversmustmakeadjustments to maintain the properpressurebalancebetweentheirlungs and the water. This changemust also take place gradually tocreateanequilibrium.If a diverwith full lungs ascends rapidly on awarm day, the volume of air in thelungscanexpandquickly.Therefore,s/hemustexhalequickly to allow gas in the lungs toescape.OTHER CONDITIONS?●Allofthesegaslawscomparepressure, volume and temperature.Butwhatabouttheamountofgas?Canyoupredictawayofexpressing all four quantities in amathematical equation?●You’ll have to figure it out!LEARNING CHECKPOINT: GAS LAWS●What two variables does Boyle’slaw compare?●What does Charle’s law compare?●What does Gay-Lussac’s lawcompare?
●What does the Combined Gas Lawcompare?OTHER CONDITIONS?●Allofthesegaslawscomparethree quantities, pressure, volumeand temperature.●But a gas sample can befurthercharacterised by a fourthquantity, the number of moles ofgas in the sampleOUR OLD FRIEND… STOICHIOMETRY!●Oneimportantquantitythatyouneed to know is that at STP, onemole of any gas will have a volumeof 22.4 L,which we can use as aconversion factorEXAMPLE:●A sample of gas at STP has avolume of 48.6 L. How many molesof the gas sample are present?SO WHEN A SAMPLE CONTAINS ACONSTANT NUMBER OF MOLES….●Wecanrelate pressure, volumeand temperature using Boyle’s,Charles’s, Gay-Lussac’s, and theCombined gas law.●But…. Not all samples contain thesamenumberofmoles,sowehave to define a new relationshipIDEAL GAS LAW●Themathematicalrelationshipbetweenpressure,volume,temperatureandthenumberofmoles of a gas.●Thislawisrelated to the otherrelationships that we learned❖Boyle’s Law-Pressure andVolume areinversely related❖Charles's Law-Volume andTemperature aredirectly related●So combining these we come upwith the mathematical expressionof the ideal gas law
PV = nRT●P = Pressure inatm●V = Volume inliters●n = Number ofmoles●T = Temperature inKelvin●R = Ideal gas constant●The value of R depends on thepressure units●Refers to the next slide for thevaluesPV = nRT1.P = pressure measured inatmosphere (atm)2.V = volume measured in liter3.N = moles of gas present4.R = constant that converts theunits.-Its value = 0.0821atm/mol.K5.T = temperature measured inKelvin(K)6.Simple algebra is employed tosolve for any of these valuesTRY ONE●What is the pressure inatmospheres exerted by a 0.500mol sample of nitrogen gas in a10.0 L container at 298 K?●What is the volume, in liters, of0.250 mol of oxygen gasat 20.0°C and 0.974 atm pressure?
●A50 L sealed cylinder contains100molesofheliumgas.Itspressure at 273 K is 44.80 atm.Whatis the change in pressurewhen the gas is heated to 500 K?●CANREALGASFOLLOWEDIDEALGASEQUATIONPV=nRT?●YES, AT LOW PRESSURE ANDHIGH TEMPERATURE!SolutionsSolutions are everywhere around us. Mostof the gases, liquids, and solids we seeare mixtures of at least one substancedissolved in another.There are different types of solutions. Theairwebreatheisasolution,primarilyoxygenandnitrogengases.Carbonmakes carbonated drinks.The ocean is also a solution, consisting ofmany ionic compounds such as sodiumchloride dissolved in water. The antiseptictincture of iodine is a solution of iodinedissolved in ethanol.Ourbodyfluidscontainwateranddissolvedsubstancessuchasglucoseandurea and electrolytes such as K+,Na+, Cl-, Mg2+, HCO3-, and HPO42-.Properamountsofeachofthesedissolved substances and water must bemaintainedinthebodyfluids.Smallchanges in electrolyte levels can seriouslydisrupt cellular processes and endangerour health.
In the processes of osmosis and dialysis,water,essentialnutrients,andwasteproducts enter and leave the cells of thebody,Thekidneysutilizeosmosisanddialysis to regulate the amount of waterand electrolytes that are excreted.Solutionscanbedescribedbytheirconcentration, which is theamountofsolute in a solution.Theserelationshipsmass%(m/m)volume % (v/v) mass/volume % (m/v)molarity(M)canbeusedtoconvertbetween the amount of a solute and thequantity of its solutionSolutionsare also diluted byadding aspecific amount of solvent to asolution.A solution is a homogeneous mixture ofone substance (solute) dissolved inanother substance (solvent) or dissolvingmedium.Solid solutions include brass, bronze andsteel.Concentration is a ratio of the amount ofsolute to the amount of solvent.Most Common Types of Solutions:THREE TYPES OF MIXTURES:Brownian Movement-the continuousrandommovementof small particlessuspended in a fluid, which arisefrom collisions with the fluidmolecules-the effect is also visible in particlesof smoke suspended in a gas-movement of pollen grains on stillwater, diffusion of pollutants in theair, diffusion of calcium throughbones-has a stirring effect which does notpermit the particles to settle,therefore stabilizing the solutionSolubility-the maximum amount of solutethat will dissolve in a givenamount of a certain solvent at agiven temperature
-Expressed in g/100 mLSaturated solution:contains themaximum amount of dissolved solute.Unsaturated solution:contains less thanthe maximum amount of solute that can bedissolved in a given amount of solvent atspecified temperature.Factors Affecting Solubility1.Nature of Solute & SolventThe strength of attractions between soluteand solvent particles determine whetherthe substance is soluble in a givensolvent.The Rule:“Like dissolves like”similarintermolecular forces form solution withone another while substances withdifferent intermolecular forces DO NOT.-Polar solvents dissolve polar andionic substances-Non-polar solvents dissolvenonpolar solutesExamples:Water (polar) dissolves NaCl (ionic)Water (polar) dissolves Ethyl alcohol(polar)Water (H-bond) dissolves sugar (H-bond)Hexane (non-polar) dissolves oil(non-polar)2.Temperature-Generally, solubility of a solid in aliquid increases with temperature.-Solubility of other substancesremains unchanged if thetemperature is increased-Ce2(SO4)3 or Cerium (III) sulfatedecreases with increasingtemperature3.Pressure- - shaking the containerof mixture4.Concentration of Solutions-solute decreases its solubility insaturated sol’Most Common Methods of ExpressingConcentrationA. Percent Concentration
B. MolarityMolarity (M) is the most common and mostuseful unit of concentration in ChemistrylaboratoryMolarity is an expression of moles/Liter ofthe solutionM= Molarityn= number of moles of soluteV= volume of the solution in liters
Preparing Solutions-You just calculated the molar massof NaCl to be 58.44 g/mol.-To determine how to make aworking solution of sodiumchloride, use the formulaIf we want to make a 200 mL of NaCl witha concentration of 5.0 M, how much of thecompound will we use?Molarity stands for moles per Liter. Thatmeans, convert 200 milliters to liters. Sowe move our decimal 3 places to the left.Thus, 200 mL is 0.2 L. Now, plug theobtainednumbersintotheformula.According to the formula, the number ofgrams needed is 5 M x 0.2 L x 58.44g/mol.Aftercancelingunitsandmultiplying these 3 numbers together, weget the 58.44 grams as the answer.That means, we will weigh out 58.44 g ofNaCl and add 0.2 L or 200 mL of water.Whenmakingasolution,thesolidisusually dissolved first in about 2/3 volumeof water. Thus, 58.44 g of NaCl will bedissolved first in only about 150 mL ofwater.Stir. When the solute is dissolved, add theremaining solution to agraduated cylinder and bring it to the finalvolume of 200 mL.C. DilutionDiluting Solutions-Stock solution is diluted to aworking concentration
-To determine how to dilute thestock solution, use the formula:M1V1 = M2V2 or C1V1 = C2V2C1- concentration of stock M1 - initialmolarityC2- concentration of diluted sol’n M2 -molarity of dilute sol’nV1- volume needed of stockV2- final volume of dilutionD. Parts per MillionSometimesweneedtodeal with verydilute solutions.Example: 0.0001% .In such cases, it is more convenient to usethe unit parts per million (ppm) to expressconcentrationIf drinking water is polluted with Lead ionsto the extent of 1 ppm, it means that thereis 1 mg of Lead ions in 1kg (1L) of water.When reporting concentration in ppm, theunits must be the same for both soluteand solution.Example:mgof solute per 106 mg ofsolution or g of solute per g of solutionSome solutions are so diluted that we usepartsperbillion(ppb)toexpress theirconcentrations.
Simple Flexing of Mental MuscleSodium hydrogen sulfate (NaHSO4) whichdissolves in water to release H+ is used toadjust the pH of the water in swimmingpools. Suppose we add 560.0 g ofNaHSO4 to a swimming pool that contains4.5 x 105 L of water at 25oC, what is theNa+ concentration in ppm?MM NaHSO4= 120.06 g/molSodium hydrogen sulfate (NaHSO4) whichdissolves in water to release H+ is used toadjust the pH of the water in swimmingpools. Suppose we add 560.0 g ofNaHSO4 to a swimming pool that contains4.5 x 105 L of water at 25oC, what is theNa+ concentration in ppm? MM NaHSO4=120.06 g/mo% CONCENTRATION
ACIDS AND BASES3 Definitions of Acids and BasesThetheoryofacidsandbaseshaschanged over time due to research andexperimentation.Arrhenius Acids and Bases - olderBrønsted-Lowry Acids and Bases - newerLewis Acids and Bases - newestArrhenius Acids and Bases●Svante Arrhenius: the first usefuldefinition in 1884●Nobel Prize for Chemistry in1903●Acid is a substance thatdissolves in water to produceH+●Base dissolves in water toproduce OH ions (OH-)Today we know that a H+ does not exist inwater because it reacts immediately withH2O molecule to give H3O+.Bronsted-Lowry (1923)●A broader definition than Arrhenius●Acid is H+ or proton donor●Base is H+ acceptor●Acids and bases always come inpairs●When HCl dissolves in water, itgives proton to water.HCl + H2O↔H3O++ Cl-Neutralizationof an acid by a base is aproton-transfer reaction in which the acidis transformed into its conjugate base, and
the base is transformed into its conjugateacid.Conjugate acid●results from a base that acquires aproton or H+ from an acid●it is a base with a hydrogen ionadded to itConjugate base●whatisleftoverafteranaciddonated a proton during a chem’lreaction or a species formed afteracidlostitsprotonsaspeciesformed by the removal of a protonfrom an acidSummary:Acid+Base⇌Conjugate Base + ConjugateAcidLewis Acids And BasesNot all acid-base reactions involve protontransfer.Acid-Chemical substance that can acceptapairofelectronsto form a covalentbond.Base-Chemicalsubstancethatcandonateapairofelectronstoformacovalent bond.Neutralization-Formation of a covalentbond between an acid and base reactant.●Lewis Acid:electron-pair acceptor=electrophile=aspeciesthatformsanewcovalentbondbyaccepting a pair of electrons duringreaction●Lewis Base:electron-pair donor =nucleophile = a species that formsa new covalent bond by donating apair of electronsA Lewis Base (B) donates it electronstoaLewisAcid(A)resultinginacoordinatecovalentlybondedcompound, also known as anadduct.●The reaction of a Lewis acid and aLewisbasewillproduceacoordinate covalent bond.●Coordinate covalent bond: a typeofcovalentbondinwhichonereactant gives it electron pair toanother reactant.●Lewis base donates its electrons tothe Lewis acid. When they do reactthis way the resulting product iscalled an addition compound, or anadduct .Lewis Acids●acid that accepts an electron pairelectrophilic (electrophile): they areelectron attracting●All metal cations are Lewis acids:they’re able to accept electronsExamples:Cu2+ Fe2+ Fe3+●Lone-pair acceptors: atom, ion, ormolecule with an incomplete octetof electrons can act as Lewis acidExamples: AlCl3 BF3 AlF3
●Molecules where the central atomcanhavemorethan8valenceshellelectronscanbeelectronacceptors, and thus are classifiedas Lewis acids.Examples: SiBr4 SiF4●Molecules that have multiple bondsbetweentwoatomsofdifferentelectronegativities.Examples: CO2 SO2ELECTROPHILENUCLEOPHILEPositively charged orneutral, but electrondeficient atom orgroup of atomsNegatively charged orneutral, but electronrich atom or group ofatomsNeutral but electrondeficient species: BF3AlCl3 FeCl3Neutral but electronrich species: H2ONH3 RNH2 ROHPositively chargedspecies: H+(hydrogen ion/proton)H3O+ (hydronium ion)+CH3 (carbonium ion)Br+ (bromonium ion)Cl+ (chloronium ion)NH4 + (ammoniumion), etc.Negatively chargedspecies:Cl- (chloride ion)Br- (bromide ion)CN- (cyanide ion)I - (iodide ion)OH- (hydroxide ion)NO2 - (nitrite ion), etc.
How do we measure the strengthof a base?• Strong base:when all molecules of abase break apart or completelydissociates in water to give off plenty ofOH-• Weak base:when only few basicmolecules dissociate in water and give offmuch less OH-Strong Acids●A strong acid breaks downcompletely in water and gives offmany H+ Ions●Are consumed to dissociatecompletely when in aqueoussolution.●When all the molecuules of an acidbreak apartWeak Acids●A weak acid only partially breaksdown. It gives off much less H+than a strong acid.●Dissociates only slightly inaqueous solution. The majority ofmolecules remain undissociated.●When a few molecules of an acidbreak apart.Characteristics of Acids•pH less than 7• taste sour• change the color of indicators >> bluelitmus turns red/pink• neutralize bases• form H+ in aqueous solution• corrosive >> react with most metals andcarbonates to form H2• good conductors of electricityCommon Acids•HCl - Hydrochloric acid- stomach acid-commerciallysoldasMuriatic acid•H2 SO4 - Sulfuric acid - car batteries• HNO3 - Nitric acid - explosives• HC2H3O2 - Acetic acid - vinegar• H2CO3 - Carbonic acid – sodas• H3PO4 - Phosphoric acid –flavorings• H3C6H5O7 - Citric acid – citrus fruitsCharacteristics of Bases•taste bitter• give slippery feel• contain Hydroxide ions (OH-)• can burn skin as badly as strong acids• react with acid to form salt and water• turnred/pinklitmus paperblue
AcidsBasesTaste sourTaste bitterNo slippery feelHave slippery feelpH < 7pH > 7Release H+ inaqueous solutionRelease OH- inaqueous solutionCorrode metalsDo not corrodemetalsReact with metalsto produce acompound andhydrogen gasDo not react withmetalsturn blue litmuspaper into pinkTurn pink litmuspaper into blueA chemical reaction between an acidand a base to produce a salt (an ioniccompound) and water• acids and bases neutralize each other•antacidtabletneutralizesgastrichyperacidity• Parietal cells in the mucosa, the innercell layer of human digestive tract, secreteHClintothestomach'slumen.Thesolution in the lumen may have a pH of 1or less - 10 times more acidic as purelemon juice.
SaltFormulaCommonNameSodiumchlorideNaCltable saltSodiumnitrateNaNO3ChilesaltpeterSodiumbicarbonateNaHCO3bakingsodaPotassiumcarbonateK2CO3Carbonateof PotashAmmoniumchlorideNH4ClSalammoniacpH•power of Hydrogen; commonly used torepresent H+ activity in logarithmic scale• At pH 7 = H+ and OH- activities areequal• A change on the pH scale by 1 pH unitindicates that the H+ activity differs by afactor of 10 (tenfold).Example:>> H+ activity at pH 4 is 10times greater than at pH 5 >> A differenceof 2 pH units, for example from 6 to 4,means that the acidity ofpH 4 is 100times greater than pH 5.
pH Values of Some CommonMaterialsImportance of pH1. pH and the body●SubstancesinthebodyhavedifferentpHvalues.Acidicconditionsinthestomach(pH~1.5) and alkaline conditions in thesmallintestine(pH~8.4)areneeded for good digestion. Slightlyacidic condition in the blood (pH~6.5) that goes to the heart andlungs is due to CO2 in the blood.2. pH and food preservation●Manyfresh food quickly go badmainlyduetomicroorganismssuch as bacteria present in food.Acidscanbeusedtopreservefoodbecausemicroorganismscannotgrow well in solutions ofquite low pH.How to measure pH?Acid-Base Indicators• are compounds that will change color inthe presence of an acid or base• Several acid-base indicators exist, eachproducing a color change at a specific pHlevel.• Litmus is a plant extract that can be blueor red/pink It turns red/pink in an acidicsolution It turns blue in a basic/alkalinesolutionACID REDBASE BLUE
Color Variation in HydrangeasSoilpH indirectly changes flower color.When the soil is acidic (pH below 7),aluminumcanbedissolvedinwatersupply making itmore available to theroots, resulting in blue flowers.Ifaluminumispresentinsmallquantities, the color is variable betweenpinkandblue. If aluminum is absent, theflowers are pink.strongly acidic soil(below pH6) blueflowers alkaline soil (pH above 7) pinkflowersAn evenmore precise wayofdetermining pHis the use a pH meter- measures small voltages in solution- calibrated to convert voltages into pH
ACIDS, BASES AND BUFFERSIn 1884, Svante Arrhenius proposed thesedefinitions:●Acid : a compound or any speciesthat increases the concentration ofH+ in aqueous solution●Base : any species that increasesthe OH- ions in aqueous solution●Arrhenius’ definition of an acid hasalready been slightly modified.●H+ reacts immediately with a watermolecule to give a Hydronium ion(H3O+).Acidicaqueoussolutiondoes not contain H+ions.●Arrhenius definitions are still valid& useful today, as long as we talkaboutaqueoussol’n.Wefrequently use H+ & proton whenwe mean H3O+. They’re generallyused interchangeably.●For instance, when HCl dissolvesin water, it reacts with water to givehydronium ion and chloride ion.●We use curved arrows to show thechange in position of electron pairsduring this reaction; the first arrowshowstheformationofanO-Hbond,thesecondshowsthebreaking of an H-Cl bonds.With bases, the situation isslightly different.●Many bases are metal hydroxidessuchasKOH,NaOH,Mg(OH)2and Ca(OH)2●These compounds are ionic solidsand when they dissolve in water,theirionsbecomehydrated andseparate:●Not all bases are hydroxides; thesebasesproduceOH-byreactingwith water molecules, here shownfAor ammonia (NH3 )●We use curved arrows to show thetransfer of a proton from water toammonia (NH3 ). The first arrowshowstheformationofanN-Hbond, the second shows breakingof an H-O bond.●the tail of curved arrow is at theelectron pair the head shows●thenew position of the electronpair
●Strongacid:onethatreactscompletelyoralmostcompletelywith water to form H3O+ ions or anacidthationizescompletelyinaqueous solution●Strongbase:onethatreactscompletelyoralmostcompletelywith water to form OHions●The 6 most common strong acidsandthe 4 most common strongbases:Weak acid●a substance that dissociates onlypartially in water to produce H3O+●an acid that is only partially ionizedin aqueous solutionacetic acid isa weak acid●in water, only 4 out every 1000molecules are converted to acetateionsConcentration●theamountofacidinagivensolutionConcentratedacidcontains large amount of acid in agivenvolume;adilutesolutioncontains a small amount of acid pHscale gauges the amount of H ionsin solution A decrease of 1 on thepH scale means a 10-fold increasein H+ concentrationWeak acid●a substance that dissociates onlypartially in water to produce H3O+ions.●acetic acid is a weak acid●in water,only 4 out every 1000molecules are converted to acetateionsWeak base:a substance thatdissociates only partially in water toproduce OHions●NH3 (ammonia) = a weak base●The position of the equilibrium for itmolecules reaction with water liestoward the left.●Example: In a 1.0 M solution ofNH3 in water, only about 4molecules of NH3 out of every1000 molecules react with water toform NH4 + and OH- .Brønsted-Lowry Acids & Bases• Acid:a proton donor• Base:a proton acceptor• Acid-base reaction: aproton transferreaction• Conjugate acid-base pair:any pair ofmolecules or ions that can beinterconverted by transfer of a proton
We can use curved arrows to show thetransfer of a proton from acetic acid toammonia. The curved arrow on the rightshows that the unshared pair of electronson nitrogen becomes shared to form anew H-N bond. At the same time that theH-N bond forms, the O-H bond breaks andthe electron pair of the O-H bond movesentirelytooxygentoform–O-oftheacetateion.Theresultofthesetwoelectron-pairshiftsisthetransferof aproton from an acetic acid molecule to anammonia molecule.Notethefollowing about the conjugateacid-basepairs.Table8.2showstheexamples of conjugate acid-base pairs.1. An acid can be + charged, neutral, or -charged examples: H3O + H2CO3 H2PO42.A base can be negatively charged orneutral examples: Cl- HCO3 - PO4 3- NH33.Acidsareclassifiedamonoprotic,diprotic,ortriproticdependingonthenumber of protons each may give up.Example:Carbonic acid loses 1proton tobecome bicarbonate ion, and then a 2ndproton to become carbonate ion4.Several molecules and ions appear inboththeacidandconjugatebasecolumns;thatis, each can function aseither an acid or a base.The bicarbonate ion (HCO3 - ) can give upa proton to become carbonate (CO3 2- )oritcanacceptaprotontobecomeH2CO3A substance that can either donate ion oraccept ion is said to be amphiprotic. Themost important amphiprotic substance isH2OWatercanacceptaprotontobecome H3O+ or lose a proton tobecome OH
Water:AnAmphiproticMolecule Watercan act as an acid by donating its protontothebaseandthusbecomingitsconjugate acid (OH- ).However, water can also act as a base byacceptingaprotonfromanacidtobecome its conjugate base, H3O+ .Water acting as an Acid: H2O + NH3 --- >NH4 + + OHWater acting as a Base: H2O+ HCl --- > Cl- + H3O+5.AsubstancecannotbeaBrønsted-Lowry acid unless it contains aHatom,butnotallHatomsinmostcompounds can be given up. Acetic acid(CH3COOH) has 4 hydrogen atoms, but itismonoprotic- it gives up only1 proton.Similarly, phenol, C6H5OH, gives up only1 of its 6 H atoms.Thisisbecausefora hydrogen to beacidic, it must be bonded to a stronglyelectronegative atom, such as oxygen or ahalogen.6.Thereisaninverserelationshipbetween the strength of an acid and thestrength of its conjugate base●The stronger the acid, the weakerits conjugate base.●HI, for example, is the strongestacid,anditsconjugatebase,Iodideion( I- ) is the weakestbase.●CH3COOH(aceticacid)isastrongeracidthanH2CO3(carbonic acid)●CH3COO-(acetateion)isaweakerbasethanHCO3-(bicarbonate ion).Acidsandbaseshaveachemicalequilibriuminsolution.Atchemicalequilibrium, theproducts and reactantshave reached a state of balance.Additionally,determiningtheacidbaseequilibriumcanhelpinpredictingtheproducts of a reaction and the relativeconcentration of the products,as wellasaidingintheidentificationoftheweaker acid and base.Equilibrium constanta number that expresses therelationshipbetween the amounts of products andreactantspresentatequilibriuminareversiblechemicalreaction at a giventemperatureHow to determine the position ofEquilibriuminanAcid-BaseReaction1.Identify the 2 acids in the equilibrium;one is on the left side of the equilibrium,and the other on the right side.
2.UsingtheinformationinTable8.2,determine which acid is the stronger acidand which acid is the weaker acid.3.Identifythestrongerbaseandtheweaker base. Remember that the strongeracid gives the weaker conjugate base andtheweakeracidgivesthestrongerconjugate base.4.The stronger acid and stronger basereact to give the weaker acid and weakerbase.Thepositionofequilibrium,therefore, lies on the side of theweakeracidandweaker base.Acid-Base Equilibrium●We know that HCl is a strong acid,which means that the position ofthis equilibrium lies very far to theright.●In contrast, acetic acid is a weakacid,andthepositionofitsequilibrium lies very far to the left.Acid-Base equilibrium favors the sideof the reaction that has the weaker acidandbase.Intheaboveexample,thereactants side would be favoredandtherewould bemore acetic acid andwater in solution, because acetic acid isa weak acid and water is a weak base.• But what if the base is not water?• How can we determine which are themajor species present?• Identify the two acids and bases andtheir relative strengths.• The position of this equilibrium lies to theright.Example:predict the position ofequilibrium for this acid-base reaction:Solution:the position of this equilibriumlies to the right.Equilibrium ConstantsTheequilibrium constantsof acids (Ka )and bases (Kb ) can be used to determinethe relative strengths of the compounds.
Theseconstants,akadissociationconstants or ionization constants, canbe used to calculate the % ionization of anaqueous solution or to determine pH.Acid ionization constant ( Ka )●Anequilibriumconstantfortheionization of an acid in aqueoussolution to H3O+ and its conjugatebase●alsocalledanaciddissociationconstantNotice the double arrows,⇌, which meanthat as the acids is dissociating, it is alsore-combining. The reaction can proceedeither forward or in reverse, depending onthe environmental conditions.What does pKa mean?The pKa measures how tightly a proton isheld by a Bronsted acid. A pKa may be asmall, negative number, such as -3 or -5The lower the pKa of a Bronsted acid, themore easily it gives up its proton.The higher the pKa of a Bronsted acid, themore tightly the proton is held, and theless easily the proton is given up.Acid Ionization Constants●Ka for acetic acid, for example is1.8 x 10-5 .●Becausetheacidionizationconstantsforweakacidsarenumbers with negative exponents,wecommonlyexpressacidstrengths as pKa where:●The value of pKa for acetic acid is4.75●Notetheinverserelationshipbetween values of Ka & pKa●The weaker the acid, the smallerits Ka , but the larger its pKaTo Reiterate:A proton, H+, is a strong Lewis acid.It attracts electron pairs veryeffectively, so much so that it is almostalways attached to an electron donor.Astrong Bronsted acidis acompound that gives up its proton veryeasily (H+donor)Aweak Bronsted acidis one thatgives up its proton with more difficulty(partial dissociation)SELF-IONIZATION OF WATER●Pure water contains a verysmall number of H3O+& OH-Ions formed by proton transfer
from one water molecule toanother●Constant called the ion productof water, Kw●In pure water, the value of KWis1.0 x 10-14●In pure water, H3O+and OH-areformed in equal amount(remember the balancedequation for the self-ionizationof water)●This means that in pure water:pH and pOH●Hydronium ion concentrationsfor most solutions are numberswith negative exponents, wecommonly express theseconcentrations as pH, where:pH = -log [H3O+]pH= -log[H+]●Just as pH is a convenient wayto designate the concentrationof H3O+, pOH is a convenientway to designate theconcentration of OH-.pOH=-log[OH-]●The ion product of water, Kw, is1.0 x 10-14●Taking the logarithm of thisequation gives:pH + pOH = 14●Thus, if we know the pH of anaqueous solution, we can easilycalculate its pOH
pH Buffer●A solution that resists changein pH when limited amountsof acid or base are added toit.-A pH buffer as an acid orbase “shock absorber”-A pH buffer is commoncalled simply a buffer-The most commonbuffers consist ofapproximately equalmolar amounts of a weakacid and a salt of theweak acid; that is,approximately equalmolar amounts of a weakacid and a salt of itsconjugate baseExample:●If we dissolve 1.0 mole of Aceticacid and 1.0 mole of itsconjugate base (in the form ofsodium acetate) in water, wehave an acetate buffer.●How does an acetate bufferresists changes in pH?●If we add a strong acid, such asHCl, added H3O+ions react withacetate ions and are removedfrom solution:●If we add a strong base, suchas NaOH, added OH-ions reactwith acetic acid and areremoved from solution:pH BuffersThe effect of a buffer can be quitedramatic●A phosphate buffer preparedby dissolving 0.10 mole ofNaH2PO4(a weak acid) and0.10 mole of Na2HPO4(thesalt of its conjugate base) inenough water to make 1 literof solution●If we mix equal molaramounts of a weak acid anda salt of its conjugate base,the pH of the solution will beequal to the pKaof the weakacid.●If we want a buffer of pH9.14, for example, we canmix equal molar amounts ofboric acid (H3BO3), pKa9.14,
and sodium dihydrogenborate (NaH2BO3), the salt ofits conjugate base●Buffer capacityis the amountof hydronium or hydroxide ionsthat a buffer can absorb withouta significant change in pH.●Buffer capacity depends both itspH and its concentrationBLOOD SUFFERSThe average pH of human blood is 7.4●Any change greater than 0.10pH unit in either direction cancause illnessTo maintain this pH, the body usesbuffer systems:●Carbonate buffer-H2CO3and its conjugatebase Bicarbonate ion(HCO3-)●Phosphate buffer-H2PO4-and its conjugatebase Hydrogen phosphateion HPO42-●Plasma proteinsProper physiological functioningdepends on a very tight balancebetween the concentrations of acidsand bases in the blood.●A variety of buffering systemspermits blood and other bodilyfluids to maintain a narrow pHrange, even in the face ofperturbations.Bicarbonate( HCO3-) is a byproduct ofbody's metabolism. Bloodbrings bicarbonate to the lungs,and then it is exhaled as CO2.Our kidneys also help regulatebicarbonate. Bicarbonate isexcreted and reabsorbed by thekidneys. This regulates yourbody's pH, or acid balance.●A buffer is a chemical systemthat prevents a radical changein fluid pH by dampening thechange in hydrogen ionconcentrations in the case ofexcess acid or base.●Most commonly, the substancethat absorbs the ions is either aweak acid, which takes uphydroxyl ions, or a weak base,which takes up hydrogen ions.BUFFER SYSTEMS IN THE BODY●The buffer systems in thehuman body are extremelyefficient, and different systemswork at different rates.●It takes only seconds for thechemical buffers in the blood tomake adjustments to pH●The respiratory tract can adjustthe blood pH upward in minutesby exhaling CO2 from the body.
●The renal system can alsoadjust blood pH through theexcretion of hydrogen ions(H+) and the conservation ofbicarbonate, but this processtakes hours to days to havean effect.●The kidneys help controlacid-base balance by excretinghydrogen ions and generatingbicarbonate that helps maintainblood plasma pH within anormal range.BUFFER SYSTEMS IN THE BODYThe buffer systems functioning inblood plasma-Plasma proteins-Phosphate-Bicarbonate and carbonic acidbuffers●Protein buffer systems workpredominantly inside cells.●Nearly all proteins can functionas bufferPROTEIN BUFFERS IN BLOODPLASMA AND CELLS●Proteins are made up of aminoacids, which contain positivelycharged amino groups andnegatively charged carboxylgroups.●The charged regions of thesemolecules can bind hydrogenand hydroxyl ions, and thusfunction as buffers.●Buffering by proteins accountsfor 2/3 of the buffering power ofthe blood and most of thebuffering within cells.HEMOGLOBIN AS A BUFFER●Hemoglobin is the principalprotein inside of RBCs andaccounts for 1/3 of the mass ofthe cell.●During the conversion of CO2into bicarbonate, hydrogenions liberated in the reactionare buffered by hemoglobin,which is reduced by thedissociation of oxygen.●This buffering helps maintainnormal pH. The process isreversed in the pulmonarycapillaries to re-form CO2,which then can diffuse intothe air sacs to be exhaledinto the atmosphere.PHOSPHATE BUFFERPhosphates are found in the bloodin two forms:●Sodium Dihydrogen phosphate(Na2H2PO4−) = is a weak acid●Sodium Monohydrogenphosphate (Na2HPO42-) = weakbase-When Na2HPO42-comes intocontact with a strong acid, suchas HCl, the base picks up a 2ndH+to form the weak acidNa2H2PO4−and sodiumchloride, NaCl.PHOSPHATE BUFFER●When a weak acid disodiumphosphate (Na2HPO4) comes incontact with a strong base, suchas sodium hydroxide (NaOH),the weak acid reverts back tothe weak base and produceswater.
●Acids and bases are stillpresent, but they hold onto the ions.As with the phosphate buffer, aweak acid or weak base capturesthe free ions, and a significantchange in pH is prevented●Bicarbonate ions(HCO3-)andcarbonic acid (H2CO3) arepresent in the blood in a 20:1ratio if the blood pH is within thenormal range.●With 20 times more bicarbonatethan carbonic acid, this capturesystem is most efficient atbuffering changes that wouldmake the blood more acidic.This is useful because most ofthe body’s metabolic wastes,such as lactic acid and ketones,are acids. Carbonic acid levelsin the blood are controlled bythe expiration of CO2throughthe lungsInRBCs,carbonic anhydrase forcesthe dissociation of the acid,rendering the blood less acidic.Because of this acid dissociation,CO2is exhaled.●The level of bicarbonate ions inthe blood is controlled throughthe renal system, wherebicarbonate ions (HCO3-) in therenal filtrate are conserved andpassed back into the blood.●However, the bicarbonate bufferis the primary buffering systemof the Interstitial. Fluidsurrounding the cells in tissuesthroughout the body.RESPIRATORY REGULATION OFACID-BASE BALANCE●The respiratory systemcontributes to the balance ofacids and bases in the body byregulating the blood levels ofH2CO3●CO2in the blood readily reactswith water to form carbonicacid, and the levels of CO2andH2CO3in the blood are inequilibrium.●When the CO2level in the bloodrises (as it does when you holdyour breath), the excess CO2reacts with water to formadditional H2CO3, loweringblood pH.●After holding breath, one feelsthe urge to increase the rateand/or depth of respiration→allows one to exhale moreCO2RESPIRATORY REGULATIONOF ACID-BASE BALANCE●The loss of CO2from the bodyreduces blood levels of carbonicacid and thereby adjusts the pHupward, toward normal levels.●Excessive deep and rapidbreathing (like hyperventilation)rids the blood of CO2andreduces the level of carbonicacid, making the blood tooalkaline.●This brief alkalosis can beremedied by rebreathing air thathas been exhaled into a paper
bag. Rebreathing exhaled airwill rapidly bring blood pH downtoward normal.Respiratory Regulation of Blood pHThe respiratory system can reduceblood pH by removing CO2 from theblood.REVIEW: BUFFERS●A variety of buffering systemsexist in the body that helpsmaintain the pH of the bloodand other fluids within a narrowrange- between pH 7.35 and7.45.●A buffer is a substance thatprevents a radical change influid pH by absorbing excesshydrogen or hydroxyl ions.●Most commonly, the substancethat absorbs the ion is either aweak acid, which takes up ahydroxyl ion (OH–), or a weakbase, which takes up ahydrogen ion (H+).●The 3 major buffer systems ofhuman body are: protein,phosphate, and bicarbonatebuffersCHAPTER REVIEW●Several substances serve asbuffers in the body: cell andplasma proteins, hemoglobin,phosphates, bicarbonate ions,and carbonic acid.●The bicarbonate buffer is theprimary buffering system of thefluid surrounding the cells intissues throughout the body.●The respiratory and renalsystems also play major roles inacid-base homeostasis byremoving CO2and hydrogenions, respectively, from thebody.CALCULATION OF pH AND pOHFORMULA:●pH = -log [H+]●pH = -log [H3O+]●[H3O+] = antilog [-pH]●pH = pH + pOH●[H3O+] = 1.0 x 10-14/[OH-]●pOH = -log [OH-]●[OH-] = antilog[-pH]●pKa = - log(Ka)●pH = pKa + log[A-]/[HA]pKa values are in table 8.3A-conjugate basedHA acid1.If we add 0.010 mol of HCl to 1L of pure water, it reactscompletely to give H3O+and Cl-.
What will be the concentrationof OH-?Concentration of H3O+[H3O+] = 0.010 M or 1.0 x 10-2M[OH-] = 1.0 x 10-14/ 1.0 x 10-2=1.0 x 10-12M answerRecall: M means Molarity = moles/LiterNote: how to press 1.0 x1.0-14oncalculator Press 1.0 then exp then-14 then=4.Aspirin, which is acetylsalicylicacid, was the first nonsteroidalanti-inflammatory drug (NSAID) usedto alleviate pain and fever. If a solutionof aspirin has a [H3O+] = 1.7 x 10-3MWhat is thepH of the solution?5. What is the pH of an ammoniasolution with [OH-] = 3.7 x 10-3M?[H3O+] = 1.0 x 10-14/[3.7x10-3]=2.7 x 10-12MNow, we enter the [H3O+] into the pHequationpH= -log[H3O+]pH= -log[2.7 x 10-12]=11.56863624or11.66. Calculate the pH of the sample ofbile having an [OH-] = 1.3 x 10-6M[H3O+]= 1.0 x 10-14 / [1.3 x 10-6]pH= -log[H3O+]= 8.11 <<<< basicCalculating [H3O+] from pH7. Calculate [H3O+] for a urine sample,which has a pH of 7.5.[H3O+] = 10-pH= 10-7.5=3.16 x 10-8[H3O+] = 1.0 x 10-14/ [OH-]
[H3O+]= 1.0 x 10-14/ [OH-]OR10.The [OH-] of an aqueous solutionis 1.0 x 10-4M.What is its [H3O+]?STRATEGY●To determine the[H+]when weknow the[OH-]we simply dividethe water constant1x10-14bythe value of[OH-]SOLUTION●We substitute the given value tothe equation11. The[OH-]of an aqueous solution is1.0 x 10-4. What is its[H3O+]?Given: Molarity of OH- is 1.0 x 10-4or 0.0003 MWe substitute into the equation:
[H3O+]= 1.0 x 10-14/1.0 x 10-4H3O+=1.0 x 10-10Mor0.0000000001 MCALCULATING pOH and pH12. The[OH-]of a strongly basicsolution is1.0 x 10-2M.Determine thepOHandpHof thissolution.pOH = -log [OH-]pOH = -log [1.0 x 10-2]= 2.00pH= 14.00 – 2.00pH=12.0013. The[OH-]of the solution is1.0 x 10-4M. Calculate thepOHandpHof this solution?pOH = -log[1.0 x 10-4] = + 4.00pH+ pOH = 14pH= 14.00 – 4.00pH+ 4 = 14pH = 10.00pH = 14 – 4 = 1014. The [H3O+] of a certainbleaching solution is1.4 x 10-9M.What is thepH? Is the solution acidic,basic or neutral?pH = -log [H3O+]= -log [1.4 x 10-9]=8.85 This solution is basic, pHis higher than 7.Note: How to press 1.4 x 10-9 on acalculatorPress 1.4 then exp then -9 then=GIVEN:pH of solutionMissing or Required:Hydronium IonConcentration [H3O+]Formula:[H3O+] = 10-pHor[H3O+] = antilog (- pH)15. What is the hydronium ionconcentration in a solution that has apH of 8.34?[H3O+] = antilog (-pH)= 10-8.34=4.57 x 10-9MOn a calculator:Pressshiftthenlogthen -8.34.Thecalculator screen displays10-8.34or"inverse" log ( - 8.34). Thenpress =to have the final answer.16. The [H3O+] of a certain liquiddetergent is1.4 x 10-9M.What is the pH? Is the solution acidic,basic or neutral?pH = -log [H3O+]= -log [1.4 x 10-9]=8.85 This solution is basic, pHis higher than 7.pHis given and the unknown ishydronium ion concentration[H3O+]17. A black coffee has5.3 pH. What is its [H3O+]? Is it acidic,basic, or neutral? Get the antilog of 5.3on your calculator. On your calculator,you may press shift log then -5.3. Theanswer is5x10-6. Thus,acidic.
[H3O+] = antilog 5.3 (shift then logthen -5.3 =)[H3O+] =5x10-6or0.000005pKa, Ka, and pHCalculate the pKa if the Ka 1.82 x10-4pKa = -log(ka)pKa = - log(1.82 x 10-4) = 3.74The smaller the pKa value, thestronger the acid.This means lactic acid, with a pKavalue of 3.86, is a stronger acid thanacetic acid, which has a pKa value of4.75.How Do We Calculate the pH of aBuffer?●The Henderson-HasselbalchEquation gives us a convenientway to calculate the pH of abuffer when the concentrationsof the weak acid and itsconjugate base are not equal.
BUFFER pH CALCULATION1.What is the pH of a phosphatebuffer solution containing 1.0 Mof NaH2PO4and 0.50 MNa2HPO4? pKa= 7.21pH = 7.21 + log 0.50/1.0= 7.21 + (- 0.30)= 6.91What is the pH of phosphatebuffer solution containing 1.0 M ofsodium dihydrogen phosphate,NaH2PO4, and 0.50 M of sodiumhydrogen phosphate, Na2HPO4?The weak acid is H2PO4- ; itsionization produces HPO4-2,theconjugate base. The pKa of this acid is7.21 (table of constant value). Givenare the concentrations of the weakacid and its conjugate base.2.Consider a formic acid-sodiumformate solution HCOOH-HCOONa having an equimolarconcentration of 0.90M.Calculate the pH of this formicacid-sodium formate solution.Given: Ka of HCOO =1.8 x 10-4Ms: M of solutionMa: M of acid3.Calculate thepH of the buffersolutionformed when 0.30M HA(Ka = 1.8 x 10-5) is added to0.20M sodium acetatepH= pKa + log Ms–log MapKa = -log 1.8x10-5= -(-4.745)= 4.7454.To 100 mL of 0.9 M formicacid-sodium formate solution,10 mL of 1.0M HCl is added,what is the pH of the resultingsolution after the equilibriumhas been established?Ka HCOOH = 1.8 x 10-4Molarity of soln= log[0.9]Molarity of acid= log[0.9]
5.Calculate the pH of a solutionwhich contains sodiumdihydrogen phosphate(NaH2PO4) and disodiumhydrogen phosphate(Na2HPO4) in equalconcentration based on thereaction below.Given: Ka H2PO4-= 6.2 x 10-86.The Buffer System in the BloodThe concentration of carbonicacid, H2CO3, is approximately0.0012 M, and theconcentration of the hydrogencarbonate ion, HCO3-, is around0.024 M.Applying the Henderson-Hasselbalchequation and the pKa of H2CO3atbody temperature, calculate the pH ofblood.[base] = 0.024 [acid] = 0.00126.1- Ka of H2CO3in blood at 37oC
FINAL QUIZ 11.The relationship between thefollowing four variables areknown as the gas laws.-PRESSURE(P),VOLUME(V),TEMPERATURE(T),AND AMOUNT INMOLES(N)2.The warning sign on the bottleinstructs that the bottle has tobe kept away from the sunlightand high temperature. Underhigh temperatures, the airmolecules in the will expand3.which can lead to the burstingto the deodorant. Which gas lawapplies to this case?-4.Gas pressure is caused by gasmolecules-5.It is the maximum possible mass ofa product that can be formed in achemical reaction. It can becalculated from the balancedchemical equation.-THEORETICAL YIELD6.How many moles of D will beformed if there are 15 moles of B inthe chemical reaction?Balanced Equation: 4A + 3B —---5C + 9D + 15E-7.Standard temperature is the valuefor experimental measurementsestablished to allow comparisonsto be made between different setsof data. What standardtemperature has been definedused by IUPAC since 1982?-0oC8.What is a mole ratio?-9.As the volume of confined gasdecreases at a constanttemperature, the pressure exertedby the gas-INCREASES10. What would be the mass in a gramof 0.5 mole of H2SO4?-49 GRAMS11. Which temperature scale isnumerically 273 higher than that onKelvin scale?-CELSIUS12. Why is stoichiometry important tothe manufacturer of chemicalproducts?-13.A25.0g of CH4is chemicallyreacted with 25.0g O2to produceCarbon dioxide (CO2) and water.What is the theoretical yield ingrams of CO2?Balanced Equation: CH4+ 2O2—-CO2+ 2H20-17.2g (not surenakalimutan kona)14. Which of these factors canincrease the pressure of the gasparticles in a closed container?-INCREASING ITSTEMPERATURE15. When the container that confines agas is heated the temperaturerises. What will happen to thevolume of the gas? The volume ofthe gas will_____-
16. What mass of H2react in thereaction that consumes 2.45 L ofN2at STP?Balanced equation: N2(g) +3H2(g)------- 2NH3(g)-17.Boyle's Law explains therelationship between the pressureand volume of an enclosed gaswhen the temperature remainsconstant. What happens to thepressure when the volume isdoubled?-18. A gas law that explains withcertainty the inverse relationshipbetween pressure and volume ofgas, as observed in themechanism of human inhalationand exhalation.-BOYLE’S LAW19. Putting a bag of potato chips into afreezer to preserve flavor is not awise idea. Much of what maintainschips’ flavor is the pressure of thebag to ensure that preservativechemicals can keep the potatochips “fresh”. Placing the bag inthe freezer causes a reduction inpressure and the bag ends uplimp. What gas law explains thegiven situation?-CHARLE’S LAW20. Standard pressure is the pressureexerted by a column of mercury atexactly at 760-MILLIMETERS HIGH21. What volume is occupied by onemole of a gas in a standardtemperature and pressure?-22.4L22. Balanced equation: CH4+ 2 O2—CO2+ 2 H2OHow many liters of oxygen gas areneeded to burn completely a 50Lof methane (CH4)?-23. In most chemical reactions, theamount of product obtained is-LESS THAN THETHEORETICAL YIELD24. Each of the flasks below containsthe same number of molecules. Inwhich container is pressure thehighest?-25. If 4 moles of A react with 15 molesof B, what is the unused amount ofthe excess reactant?Balanced Equation: 4A + 3B → 5C+ 9D + 15E26. Charles’s Law is also known as bywhich name?-LAW OF VOLUMES27. When a gas is compressed, whichwill the result be due to anincrease in the number of collisionsof gas particles on the walls of thecontainer?-INCREASE IN ITSPRESSURE28. What gas law is closely associatedwith the function of hot air balloon?-CHARLES’S LAW29. Which of these quantities will occurwhen there is a constantbombardment of the walls of thecontainer by moving gasmolecules?-AIR PRESSURE
30.If 30 grams of a compound contain1.5 moles, what is the molar massof the compound?-31. If the molar mass of Silver (I) oxide(Ag2O) is 231.735 g/mol, howmany moles of Silver are producedin the decomposition of 1kg Silver(I) oxide (Ag2O)?Balanced equation: 2Ag2O → 4Ag+ O2-32.Silver chloride, AgCl, is anantiseptic used in some bandagesand deodorants. If we want to besure that all AgNO3is used up,then we have to make ___ thelimiting reactant by adding____ ofit that the other reactant,considering that the mole ratio is1:1Chemical equation: KCl + AgNO3— AgCl + KNO3-AgNO3, Less33. A mass of 25.0 g Hydrogenfluoride is reacted with 25.0 gSilicon dioxide. Which is thelimiting reactant based on theequation given below?Balanced equation: 4HF + SiO2→ SiF4+ 2H2O-34. Ethylene (C2H4) reacts withhydrogen chloride (HCI) formingethyl chloride (C2H5CI). If thestarting quantity is 15g for eachreactant, how many grams of theexcess reactant remain after thereaction?Balanced equation: C2H4+ HCI —C2H5CI-4.38gC2H435. Each of these flasks contains thesame number of gas molecules,but different temperature. In whichflask will the pressure be thelowest?-FLASK 136. Balanced equation: 2H2+ O2→2H2OWhat mass of O2is consumedwhen it is reacted with 6.86 g ofH2?-37. When real gases are chilled to verylow temperature, they exert a____amount of pressure in a containeras compared to an ideal gas.-LESSER38. Ethylene (C2H4) reacts withhydrogen chloride (HCl) formingethyl chloride (C2H5Cl). Calculatethe theoretical yield if the startingquantity is 15g for each reactant.Balanced Equation: C2H4+ HCl→ C2H5Cl-39. The Combined Gas Law isexpressed in an equation: P1V1/T1= P2V2/T2What must remain constant for thegiven equation to be true?-NUMBER OF MOLES40. The gas effusion rate is directlyproportional to the average velocityat which the gases move. Gas ismore likely to pass through anorifice if its particles are moving atfaster speeds. Which of thesefactors can affect th effusion rate ofgas?-MOLAR MASS
41. How many grams of Sulfur arerequired to combine with Aluminumto prepare 4 moles of Aluminumsulfide (Al2S3)?Balanced equation: 2 Al + 3S →Al2S3-42. Boyle’s law relates to the way twogas properties change whenanother property remains thesame. What are these twochanging properties?-PRESSURE ANDVOLUMEQUIZ #2What is the volume of a 0.2 M AgNO3solution containing 8.5 grams of AgNO3?-0.25LWhat mass in grams of NaOH must beadded to prepare 250 mL of 0.10 Msolution?-1.0 gTo form a solution, the solute must-Be less concentrated than thesolventPotassium alum or potassium aluminumsulfate dodecahydrate KAl(SO4)2 .12H2Ois a hydrate which means that thecompound has water molecules trappedwithin its crystals. Locally known as'tawas', this hydrate will release somewater of crystallization upon heating. Whatmass of this compound is required toprepare 50.0 g of a 12% mixture at roomtemperature? What mass of water wouldbe added to make the said mixture-6 g; 44 g waterAn intravenous (IV) solution contains100.5 mL water and 5.10 g glucose with aknown density of 1.56 g/cm3. If the molarmass of glucose is 180 g/mol, what is themolarity of the solution?-0.28 MIt refers to the maximum amount of asubstance that will dissolve in a givenamount of solvent at a specifiedtemperature.-saturationA 5% by mass can be obtained bydissolving-5g of solute in 100g solventIf a crystal of solute was added to each ofthe following types of solutions, whatwould happen?-Unsaturated – solute will bedissolvedCalculate the w/v % of each of 623 mg ofcasein in 15.0 mL milk-4.15 %Generally, the solubility of a solid in aliquid increases with temperature. Whichcompound is excluded from thisgeneralization?-Ce2(SO4)3As we dilute a solution, its volume-Increases and molaritydecreasesWhich sugar solution is mostconcentrated?-10.0g / 100Which solvent contains as much of asolute as it can hold?-SaturatedThe following are solutions except-paint
What volume of a 5.0 M solution isrequired to dilute to 0.1 L of 0.25 Msolution?-5 mLIf a concentration label says 6.0 M in a2-Liter solution of water, how many moleshave been dissolved?-12 molesWhich component of a solution takes thebiggest part?-SolventWhat volume of a 15 M NH3 solution isneeded to prepare 50.0 mL of a 6.0 MNH3 solution?-0.02 LWhat is the w/v % of 74 mg of vitamin C in250 mL of orange juice?-0.030 %The higher the value of molarity, the_______ is the solution.-More concentratedIt is a physical property of a substancethat enables its particles, in maximumamount, to mix and blend with a givenamount of solvent at a specifiedtemperature.-SolubilityWhen a solution is diluted, which of thesevalues will remain constant?-Moles of soluteWhich solution contains the maximumamount of solute dissolved in a solvent?-SaturatedWhat relationship exists between the finalvolume and the final concentration of thediluted solution?-Inverse proportionalityA bottle contains 59 mL of lemon extractsolution. If the extract contains 49 mL ofalcohol, what is the % by volume of thealcohol in the solution?-83.0%It generally refers to a solid solution.-AlloyWhich sugar concentration can render themilk tea the sweetest taste?-3.8 MThe concentration of a mixture can beincreased in which of the following ways?-Adding more powder "solute"A clogged sink can be fixed by a drainopener labeled 2.8% sodium hydroxide(NaOH) solution. This means that thebottle contains 2.8 g of NaOH for every-100g of solutionDetermine the w/v % of 3.25 g of sucrosein 186 mL coffee.-1.75%Identify the solute and solvent in thepreparation of the solution that follows.435 mL of 1.8% v/v solution of Ethylacetate (C4H8O2) and water-solute = 8.0 mL Ethyl acetate;solvent = 427 mL waterIt is the continuous random movement ofsmall particles suspended in a fluid, whicharise from collisions with the fluidmolecules.-Brownian movementThe term dextrose continues to be used torefer to glucose solutions administeredintravenously for fluid or nutrientreplacement. What is the mass in gramsof dextrose, C6H12O6, in a 1.5 L dextrosesolution having a concentration of 0.148M?-40.0 g
A substance that is being dissolved andthe part of a solution in a lesser amount-SoluteIt is the ratio of the amount of solute to theamount of solvent.-ConcentrationThe 3 types of mixtures are primarilyclassified in terms of-Particle sizeQUIZ #3Which of these compounds is amonoprotic acid?-CH3COOHWhich of these expresses the strength ofa weak acid?-ionization constantWhich substance has the lowest pH, thusmost acidic?-BatteryWhich is the most acidic?-vodka with [H3O+] = 5.01 x 10-4The normal pH range of human blood?-7.35 - 7.45It is defined as an acid that gives up itsproton with more difficulty.-weak Bronsted acidWhich of these solutions has the lowestpH at 25 C?-0.2 M Benzoic acidAside from water, which among thesesubstances is both an amphiprotic and anamphoteric compound as shown on theTable 8.2 of Acid and Conjugate Base?-HCO3-conjugate baseWhich of the following weak acids ionizesto give the strongest conjugate base?-HCNGiven the chemical reaction below, whichone applies to water?-Arrhenius baseHydrogen ions (H+) immediately react withwater molecules. After the completedissociation of HCl in an aqueous solution,which species has become the mostabundant in the solution?-H3O+What acid dissociates completely insolution and generates a proton from eachacid molecule?-H3PO4Which statement describes the limitationof Arrhenius' concept of acids and bases?-Acids and bases are defined onlyin terms of their reaction toaqueous and gaseous solutions.Sodium hydroxide, NaOH, is a strongbase. What is the pH of a 0.001 M sodiumhydroxide, OH-, solution?-11Buffer is-a weak acid or base.Breathing into a small paper bag duringhyperventilation is a conventional practiceof putting some of the lost CO2 back intothe lungs and blood. What life-threateningcondition will result if enormous CO2molecules are lost and not replaced in theblood?-Alkalosis
Solution is a(an)-evenly distributed mixture of two ormore substancesWhat is the pH of the solution if thehydroxide ion, OH-, concentration is 1.0 x10-6?-8The ion product of water, Kw, is 1.0 x10-14 which can be expressed as-Kw = [H3O+] [OH-] = 1.0 x 10-14Which concentration is increased by acidsin water?-hydroxide ionsWhich of these pH values indicates agreatest amount of alkaline or basemolecules that dissociate partially?-13.7Water can either donate or accepthydrogen ions. Which is the accurate termthat applies to water in this case?-AmphiproticWhat will happen if the hydrogen ionconcentration is lowered?-The pH will become higher.Identify the accurate statement thatdescribes the chemical equation below.-After the reaction, HCl istransformed into hydronium ion, astrong acidic substance.The Arrhenius theory of acid and baseapplies only when an acid or a base isdissolved in a solution that contains-WaterWhat is the basis of classifying acids asmonoprotic, diprotic, or triprotic?-number of donated H+At higher altitude, it takes _____ time tocook meat because water boils at _____temperature.-longer; higherWhich acid completely ionizes in anaqueous solution?-strong acidIt is a byproduct of our body's metabolism,transported by blood to the lungs, andexhaled as CO2.-Carbonic acid (H2CO3)The buffer systems given below, exceptone, are the functioning buffer systems inour blood plasma.-hemoglobin bufferGiven the pH of the various body fluids,which body fluid contains the leastconcentration of OH- ?-cerebrospinal fluid -pH 7.3An increase of one unit on the pH scalerepresents a tenfold increase in theconcentration of hydrogen ions in asubstance. How much greater acidity isthere in tomatoes (pH 4.3) than rainwater(pH 6.1)?-10 timesWhich set of conjugate bases matcheswith these acids: water, acetic acid, andethanol?-hydronium ion, ammonium ion,ethoxideIt is a symbol indicating that as the acid isdissociating, it is also re-combining, andthe reaction can proceed either forward orin reverse, depending on theenvironmental conditions.-⇌
What is the general condition of the soil'spH when Hydrangea bears brightpink-colored flowers?-AlkalineGiven the pH of the various body fluids,which body fluid contains the greatestconcentration of H3O+ ?-stomach acid - pH 1.4It is a substance that readily conductselectricity and vigorously reacts with mostmetals to produce hydrogen gas.-AcidIt is synonymous with Hydrogen ion, H+.-ProtonWhat is the pH of the solution if thehydroxide ion (OH-) concentration is 0.01M?-2If the concept of acids and bases byBronsted-Lowry shows the transfer of H+ ,what about Lewis'?-transfer of electron pairThe higher the pKa of a Brønsted-Lowryacid,-the more tightly it holds its proton.The lower the pKa, the stronger the acid.The Ka of acetic acid is 1.8 x 10-5 whilethat of the carbonic acid is Ka = 4.3 x10-7. Which between the 2 acids is moreacidic?-acetic acidAll Arrhenius acids are Brønsted-Lowryacids, and all Brønsted-Lowry acids areLewis acids (and likewise for bases). Butnot all Lewis acids are either Arrheniusacids or Brønsted-Lowry acids.-CorrectArrhenius definition of acids and bases isof historical interest, but the highlyrecognized most inclusive concept wasconceptualized by--Brønsted-LowryIn acid-base concept, which is used toindicate the solution's concentration?-PercentIn the given chemical equation below,which holds true for hydrogen sulfate?-It reacts as acid.Water takes a long time to heat up andcool off due to the huge amount of energyit absorbs.-water polarityThe respiratory tract can adjust the bloodpH upward in minutes by exhaling CO2from the body. Which helps maintain thisfunction?-acid-base regulatory systemWhich is true about the H+ concentrationof a solution with a pH 11?-1 x 10-11 moles/literWhat is the pH of the solution if thehydrogen ion (H+) concentration is 1.0M?-0Which among these analgesics andantipyretics is the most acidic?-2-Acetoxybenzoic acid or Aspirin,pKa = 3.49Of these compounds, which has thehighest pH value, thus least acidic?-Hydrochloric acid (HCl)A solution with a lower hydrogen ionconcentration than that of pure water hasa pH that is-Yehey tama ako
-greater than than 7.What makes water unique among allliquids?-It demonstrates the universalsolvency among all liquids.Ice floats on water because-water expands when it freezesAt what temperature does water boil in anarea elevated at 3,048 meters above sealevel?-94°CWhat property of water makes it resist thedrastic change in temperature therebyprotecting the aquatic organisms from theextreme changes of environmentaltemperatures?-high melting and boiling pointsWhich condition is most accurate aboutthe adaptive mechanism of individualsresiding in high altitude area or highlyelevated place with a dramatic fall inoxygen gas?-increased concentration ofhemoglobin in the bloodWhat will occur when the atmosphericpressure equals the equilibrium vaporpressure?--FreezingAs atmospheric pressure decreases, theboiling point of water