6.03 Pre Lab

Marwah Alabbad
Post lab
10/21/15
Question 1:
1. Experiment 1:
Number of trails NaOH concentration (M) Volume of HCl solution (mL) Initial volume of NaOH(mL) final volume of NaOH(mL) The volume of NaOH to titrate HCl (mL) Concentration of HCl (M)
1st 0.1023 25.0 10.05 36.12 26.07 0.085
2nd 0.1023 25.0 5.74 31.40 25.66 0.105
3rd 0.1023 25.0 9.84 35.52 25.68 0.105
First trail calculation:
0.02607L× (0.1023mole NaOH/1L)×(1 mol of HCL/1 mol of NaOH)×(1/0.025)= 0.085M of HCl
The average HCl concentration of the three trails is = 0.098 M
2. Question 2:
Experiment 2:
The acidity and vinegar, the type of vinegar we used was Kroger distilled white vinegar, and the acidity of the vinegar was 5%
Trails Dilution of original vinegar solution. Volume of

To find the mass percent of acetic acid in vinegar, the molar mass of acetic acid is 60.05 g/mole, and 1.00 g/mol of density, then
0.96 mol×(60.05 g/1 mol) = 57.65 g
57.65 g/1000= 0.0576 ×100 = 5.76%
The average mass % of acetic acid in vinegar = 5.53%
The average % of acetic acid was 5.53%, which is close to the acidity of the vinegar that was taken in the lab which was 5%, for the different percent we had it could be because of errors in calculations or errors in collecting data.
3. Question3:
Experiment 3
The unknown acid sample was 1
• Monoprotic Acid
Trails Initial NaOH solution (mL) final NaOH solution (mL) The volume of NaOH to titrate the acid (mL) Amount of Unknown Acid sample 1 (g) The moles of the Unknown Acid (mol) Molar mass of the Unknown Acid
(g/mol)
A 3.38 28.31 24.93 0.150 0.0026 57.69
B 0.18 29.32 29.14 0.175 0.0029

Question 4:
List the 3 errors;
• Adding too many drops of NaOH at the same time would affect the results because we can’t determine the exact equivalent point when the color changed. The results won’t be accurate and that will affect all the data that are dependent on the amount of NaOH to titrate.
• Other error could be the hardness to notice a color change; we always use a white paper under the flask to determine when the color changes right away. And if we don’t use the white paper it will be hard to determine the color change and the amount of NaOH that was used to titrate it.
• Also other source of error could be by not rising the burette with NaOH before we fill up with it, or it maybe they were rinsing it with a lot of NaOH which could affect the data recording for NaOH amount of titration.
5. Question 5:
a) As mentioned in the manual, we have the ratio (K/H+ ), if H+ was lower than K then the equivalent point will be achieved and it will change color. And if H+ was more than K then the solution we are titrating will be the same, the equivalent point won’t be achieved, and it will be acidic solution. And to find the value of H+ is by having the value of pH, therefore the pH has changed from 7 to 9, which is by shifting from 10-7 to 10 -8 by adding the 0.01 of the base, and it will shift again from 10 -8 to 10 -9 by adding another 0.01 of the base to the solution , the different that’s added between the two shifting are close to each other which indicates that the