Understanding Electrochemical Cells: Reactions and Observations

School

University of Ss. Cyril and Methodius**We aren't endorsed by this school

Course

MATH CHEMI EG.202

Subject

Chemistry

Date

Dec 11, 2024

Pages

Uploaded by PrivateAtom15534

d Refer to the following simple cell. ).fi. 4 ‘)_H"L,. H, s ® H——-‘——J ’ , o s V bubbles of —<Gie & = dilute sulphuric acid hydrogen —h ) \ - ) Hydrogen gas is liberated at the silver electrode. (a) What is the direction of electron flow in the external circuit, from silver tq zinc, ¢r from zinc to silver? (L\y\(/ 1 3\\\/6( \/ ®) @) Isth r electrode positive pole or negative pole? P v (i) Is the silver electrode anode or cathode? (U\O &' (iii) Write an ionic half-equation to represent the ¢ taking place at the silver electrode. 'LH 1 2{ >y \’f / (¢) (i) Is the zinc electrode positive pole or negative pole? {\ejafi\& (i1) Is the zinc electrode anode or cathode? M (iii) Write an ionic half-equation to represent the change which is taking place at the zinc electrode. Z“’) rZ»r\ TZ/L / / (d) Write an ionic equation to represent the overall change. 1H+ ‘FZ\ N - 'HLT 2;(\”' (¢) The milliammeter reading drops after the cell has operated for some time. () Suggest a hypothesis to explain why the current decreases. \&S %l'\fi.—’&“ fW&n&Q&(’K (1) Describe how you would verify your hypothesis. (12 M) >< W Mg? (UN YA AKIg> \“\9\/

Conslder the simple ¢chemical ¢oll shown below, digital multimeter (an voltmeter) F?F flow of electrons ﬂ* SRt ] (1] P — metal Y electrode W /I\ clectrode B | S 1 I (R S e ssmie bridge | = : { AUIPNALE KONIHON e P 2225 ridg nitrate solution of metal ,\' of metal Y (@) Which metal is more reactive, X or 1? Explain, a "I"{w J‘r-m YL X, Y ;\Vo}\\‘r\ tcmx\ °§Q,€(L&( N o e Ul (1) Which ix the positive pole, metal Xor 1? x/ (©) () How can a salt bridge be prepared? U \ Sl NG, e v ‘ W Sv\‘,\*‘LN\}\ ‘ | [ ! i\T

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a4 Which of the tollowing statements vonvering the slesiynlysin of soppeit 1) siibphnt solution mlnmm\l\\ho\vlcvumlon e gonvet) A (1) The phl valwe of the solution aradwally devrsines, S “ s (2) Copper is deposited at the eathode, [/ \f ( K / ‘}_ () / 1l (3) Hydrogen gos is given oft'al the unml% « . @(l)nna (2) only F) o 0 (D) and () only C. (2)and (V) only \ /H-" ' - NE B T -

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'I F J 6 f ® '/. (a) Chloroform is commonly used as solvent and anaesthetic. The systematic name of chloroform = !ng' hloromethane. (1) Draw the three-dimensional structure of a trichloromethane molecule. H | (ii) The intermolecular forces between chlorofonm molacnles are caly vam der Wials” Sress However, it is said that hydrogen bonding occurs when chlorofomm == -xdvn;rse’fi? With the help of a diagram, suggest a possible reason for this phemomenon. 'l_, ‘..2. ) a 4 ‘ Y ,'C"\C/O \/C/U AB 7 d« \3(4,”, @%H - \/\QQ)‘ 1o ior O™ 3 \\L’C‘\s |5 & cL(‘l\Q o r oy (‘(Q({m\( m ‘“* L/WAN?QI\ (it'hJ Mok VX0 “"f"&w’)\ > IR Z A-Y(lf'&}(_n A)’lﬂl \Y

(b) Many alcohols, including ethanol, are soluble in water, (1) (1) Explain, with the aid of a diagram, why ethanol is soluble in water, The solubility of hexan-1-ol and hexane-l,6-diol in water is shown in the table below : Alcohol Solubility in water /g dm™ Hexan-1-ol Hexane-1,6-diol 500 5.9 o VIV, Explain the difference in solubility of hexan-1-ol and hexane-1,6-diol. }UUNCV\.—l —O‘ Aaj 3"‘7’ one /\74/0)(7, j{b“f’ M ‘W\e-’,g‘}p’ @ Lll(;.‘ Lo, 6@7 /\(&ro%h IJ’ON&J w\U\ Ve 5 1) herd- P his 2 Ao 9o a1 »-AQ /WW\LL»\LQ:S PRNG

(a) Some bacteria can oxidise methane to carbon dioxide in the absence of oxygen. It has recently beer reported that the process involves a reaction between methane and nitrite ions in acidic conditions. The half-equation for the oxxdano%\f metlmue 1s&€ven below. 2/ 3 cn.+2u,o~co;+su+ 33\ 41_& : 3 (1) Wnte a half-equanou for the reducnon of NO;™ in acidic coudmons to give N». ) (1) b\By comb§m02 the half-equanons or otherwise, wnte down the ovemll equation for the reaction between methane and nitrite ions in acidic conditions. +$NO; + gyt Cl ZCHr N gt —>3W, TN, +[90H,0 7 (2 marks ®) This question is about the compounds of the nzf'?n EF'T vanadium (V) and its ions. (@) Give the oxidation state of vanadium in [\ow IS I\uj ke B oxr\im St‘g (1) Use the following information to identify the species tlmt can be used to reduce VO:" ions u VO?** in aqueous solution and no further. Explain your answer. Ionic half-equation Oxidising agent Reducing agent Zn**(aq) + 2e” S Zn(s) 2+ + - o— 3+ Increasing VO?**(aq) +2H*(aq) + ¢ s V3#*(aq) + HxO(l) Bession oxidising power Fe'*(aq) +e” s e**(aq) reducing power VO,*(aq) +2H*(aq) + &~ = VO*(aq) + H:0(1) Cly(aq) +2e- = 2Cl(aq) Species used : 1\ ...............................................................................................................ERANHTIONLT aromsrnnssntsassncom svmsmpimmasi s+ mmviatsyavx e ST oo ity s S oS sureenvnss ----------------------------------------------------------------------------------------------------------------------------------------------

8. f[ , ) ‘ Mad \Qd\l Nitrosyl fluoride (NOF) 1s a colourless gas at room uons ) (@) Draw tfie three-dimensional stmc\:ure of nitrosyl fluoride. M$ M e NS Wﬂ | ify, with explanation, the polar b;\s‘d(s) in nitrosyl fluoride. 0 2‘/\\: N e el onyulive the N \/I$_—/D ok N\"\’ & marks) (c) State and explain whether nitrosyl fluonde iy/a polar molecule. N= O dalle bl o V€ ) /\} CMIVW& IMLN\LL ou/(v fo T Q( (1 mark) (1 mark)

- S’ W Cees A\ electrode made of /> metal P o carbon electrode R + @g electrode made of ___ ——carbon clectrode § i 4 o X (@) %0 - — copper(ll) sulphate dilute sulphuric acid — o s e o solution Sct-up X Set-up Y In the above diagram, P and Q are two different metals. When the circuit is closed, a current flows in the external circuit. After some time, 0.36g of copper is deposited on the carbon electrode R. (i) (1) Whatisthe direclionlhc external circuit? Explain your answer. (ii) After the circuit has been closed for some time, what would be observed (1) at the carbon electrode § ? (2) in the copper(ll) sulphate solution? (iii) What is the function of set-up X in this experiment? (iv) Which of the metals, P or Q, occupies a higher position in the electrochemical series? Explain your ANSWer. DDESTAREED, X e f— S\>K->@\ i) I) coLw/Lfi{S 94 Lubhlayg Con oLy(\)‘}/ “ 7« .twr\ ’?ﬂm L (fi W\AS m) C ‘(t}'é( 'tr‘r'v\‘&t Q’quj ‘F"f‘ QL@W “w) @\ / 3

10. (0( a. A student used the set-up shown below to prepare hydrogen and chlorine by electrolysis of a very dilute sodium chloride solution. Contrary to the student’s expectation, a colourless gas X instead of chlorine was liberated at the anode. X hydrogen very dilute sodium chloride solution carbon electrode carbon electrode / (i) Whatis X? 'Dyy N\ (ii)) Suggest a chemical text for X. \7 ' M!\,\\j s Fl frfb f"«lY \5 _ (2 marks) b. The experiment in (a) was then modified so that hydrogen and chlorine were groduced at the cathode a anode respectively. _tm C (i) Sugeest how the experiment could be modified. L PhEA a \/ . \ 21l (ii) Deduce the ratjo of the theoretical volumes of hvdrogen and chlorine produced. : "l:q'9 Ch+ e (iii) With the help of a chemical equation, explain why the volume of chlorine collected is signiticantly smaller than the theoretical volume. M‘(’, - - (\ (6 marks) K © oy L o o e

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12. An clectrolysis experiment is conducted using the set-up shown be ow: _f‘ - Nt C Cl(aq) + litmus indicator 7 carbon electrode X carbon electrode Y What are the expected colours around X and Y after the experiment has been conducted for some time ? X Y fi yellow red /B. red blue @5 blue red >< red yellow