Lab Report Molar Mass of Citric Acid PDF

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Download Lab Report Molar Mass of Citric Acid PDF

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Lab Notebook/Report Exercise Name: Ashley Tong 

Section:

13

Table 1: Molar Mass of Citric Acid Trial One:

Trial Two:

Trial Three:

Trial Four:

Trial Five:

Trial Six:

Mass of weight boat (g):

1.256

1.254

1.258

1.259

1.256

1.257

Mass of weight boat + citric acid (g):

1.417

1.418

1.421

1.422

1.421

1.419

Initial volume of NaOH (mL):

1.20

1.45

1.89

2.45

3.01

3.12

Final volume of NaOH (mL):

26.50

31.15

27.19

30.95

32.71

28.52

Color of the titrated solution:

Pale Pink

Hot Pink

Pale Pink

Hot Pink

Hot Pink

Pale Pink

Trial One:

Trial Two:

Trial Three:

Trial Four:

Trial Five:

Trial Six:

Amount of NaOH used (mL):

25.30

29.70

25.30

28.50

29.16

25.40

Moles of citric acid used (mol):

8.38 x 10^-4

8.53 x 10^-4

8.48 x 10^-4

8.48 x 10^-4

8.58 x 10^-4

8.43 x 10^-4

Moles of NaOH used

0.6325

0.7425

0.6325

0.7126

0.7291

0.6350

Calculated Results Table:

(mol): This experiment was done without a partner and at home instead of in a lab. 3 NaOH (aq) + H₃C₆H₅O₇ (aq) → Na₃C₆H₅O₇ (aq) + 3 H₂O Calculated results: Average Molar Mass: (192.124 g + 192.263 g + 192.217 g + 192.217 g + 192.308 g + 192.171 g) / 6 = 192.217 g Trial One: 0.161 g / 8.38 x 10^-4 mol = 192.124 g Trial Two: 0.164 g / 8.53 x 10^-4 mol = 192.263 g Trial Three: 0.163 g / 8.48 x 10^-4 mol = 192.217 g Trial Four: 0.163 g / 8.48 x 10^-4 mol = 192.217 g Trial Five: 0.165 g / 8.58 x 10^-4 mol = 192.308 g Trial Six: 0.162 g / 8.43 x 10-4 mol = 192.171 g Standard Deviation: √((192.124 - 192.217)² + (192.263 - 192.217)² + (192.217 - 192.217)² + (192.217 - 192.217)² + (192.308 - 192.217)² + (192.171 - 192.217)²) / 6 - 1 = 0.059387 Average Molar Mass of Good Trials: (192.263 + 192.217 + 192.308) / 3 = 192.263 Standard Deviation of Good Trials: √(192.263 - 192.217)² + (192.217 - 192.217)² + (192.308 192.217)² / 3 - 1 = 0.03715 Percent Error: (192.263 - 192.124 / 192.124) x 100 = 0.0723% Discussion Questions: 1. Student B measured the citric acid fairly well, only being a few thousandths off from the goal of 0.160 g per measurement. Both the accuracy and precision because of this were pretty good, especially considering there was such a low percent error for the molar mass of citric acid. The student used 0.160 g of citric acid and the lab instructions also said to use this so I do not see any significant systematic errors here. As for random errors, these are unavoidable and should be accounted for in all trials. 2. a. The molar mass would be too low if the standardized NaOH was exposed to air after the standardization. This will happen because the NaOH solution would react with CO₂ in the air leading to a lower volume resulting in a lower concentration. b. The molar mass would not change if the standardized NaOH was exposed to air before the standardization. The loss of NaOH would already be accounted for in the calculation. 3. If you used 50 mL instead of 25 mL of water, the accuracy of molar mass would not be significantly affected by the change in procedure. The water is only used to dissolve the acid in the solution so the volume of it is unimportant. 4. If the buret was rinsed with DI water and then filled with the NaOH solution without rinsing with NaOH solution first, the calculated molar mass as a result would be lower. Since the volume of the NaOH solution increased, the molarity of NaOH would decrease. This would require a higher volume of NaOH solution resulting in a higher amount of moles of acid, ending in a lower molar mass....