Determination of Citric Acid in Lemon Juice Lab PDF

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report for lab 2...

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Instructions: Please complete the following fields, corresponding to Experiment 2 in Chemistry 1000H. If you have any questions, please contact the laboratory coordinator.

Name: Jorja Gallivan

Student #: 0668356

Partner Name: Holly Hodgson

Experiment Date: Oct. 11th, 2019

CHEM1000H – LAB REPORT 2 1. Raw Data (report all values to the appropriate significance) A: Preparation and Standardization of a Solution of Sodium Hydroxide Mass of 250 mL beaker (grams): 111.4353 Mass of 250mL beaker with NaOH (grams): 116.5278 Table 1: Data for the preparation of a standard solution of sodium hydroxide Sample 1

Sample 2

Sample 3

Mass of weigh paper and oxalic acid (grams)

0.8177

0.8212

0.8166

Mass of paper after transfer (grams)

0.0472

0.0249

0.0237

Table 2: Data for the standardization of a solution of sodium hydroxide Trial 1

Trial 2

Trial 3

Initial burette reading (mL)

0.85

1.30

1.05

Final burette reading (mL)

30.35

30.85

38.15

B: Verification of Titration Technique

Table 3: Data for the verification titration Trial 1

Trial 2

Trial 3

Initial burette reading (mL)

0.65

0.75

0.55

Final burette reading (mL)

22.55

21.3

22.05

C: Determination of Citric Acid content in Lemon Juice Table 4: Data for the determination of citric acid content in lemon juice Trial 1

Trial 2

Trial 3

Initial burette reading (mL)

0.55

0.50

0.65

Final burette reading (mL)

18.30

19.05

18.00

2. Calculate the concentration of your stock NaOH solution showing complete sample calculations for one of the trials. Table 5: Determination of the concentration of the standardized NaOH stock solution Trial 1

Trial 2

Trial 3

Mass of oxalic acid used (grams)

0.8177

0.8212

0.8166

Moles of oxalic acid

0.8177 /

0.8212 /

0.8166 /

70.0376

70.0376

70.0376

=0.011675

=0.011725

=0.011659451

Moles of NaOH (from balanced chemical

0.011675*2

0.011725*2

0.01165945*2

equation with oxalic acid)

=0.02335

=0.02345

=0.0233189

Volume of NaOH titrated (L)

29.50 / 1000

29.55 / 1000

37.1 / 1000

=0.02950

=0.02955

=0.0371

0.02335 /

0.02345 /

0.0233189 /

0.02950 =

0.02955

0.0371

0.791525423

=0.79661591

=0.62854178

Concentration of NaOH solution (mole/L)

Average NaOH concentration (mole/L):

0.791525423+0.79661591+0.62854178 3 =0.738894371

Standard Deviation:

0.078058724

3. Determine the concentration of the provided citric acid sample and compare it to the value given in the lab using error analysis. (Show a complete sample calculation for one of the trials) `````````` Table 6: Analysis of citric acid standard solution via titration with NaOH Trial 1

Trial 2

Trial 3

Volume of NaOH titrated (L)

0.02950

Moles of NaOH

0.791525423 0.79661591 * * 0.02950 0.02955 =0.023349999 =0.02354

0.62854178 * 0.0371 =0.0233189

Moles of Citric Acid

0.023349999 /3 =0.00783333

0.0233189 / 3 =0.007772966

Mass of Citric acid in the sample (grams)

192.1214 * 192.1214 * 0.00783333 0.007846666 =1.504950326 =1.507512457

192.1214 * 0.007772966 =1.49335311

Concentration of citric acid (gram/L)

1.504950326/ 1.507512457 / 0.025 0.025 =60.198 =60.300

1.49335311/ 0.025 =59.734

Average citric acid concentration (gram/L)

60.198+60.300+59.734

0.02955

3 =60.077 Standard Deviation:

0.211738045

Concentration of provided citric acid

25.88

solution (gram/L)

0.02354 / 3 =0.007846666

0.0371

Error (gram/L)

60.198— 25.88 =34.318

60.300—25.88 =34.42

59.734—25.88 =33.854

Relative Error (%)

34.318 / 25.88 = 133%

34.42 / 25.88 =133%

33.854 / 25.88 =131%

Average Relative error (%)

132.33%

4. Comment of the accuracy and precision of this titration technique According to our table and calculations, the accuracy and precision of this titration technique is very poor. Calculating our error led to a percentage over 100% meaning there was either an error in measurements during the experiment, or the accuracy and precision were just very inaccurate resulting in the extremely large relative errors. Since our calculations were done in the correct way, this leads to the strong belief of the error coming from measurements and/or other parts we completed IN the lab. 5. Determine the concentration of citric acid in lemon juice and compare it to the value given in the lab using error analysis. (Show a complete sample calculation for one of the trials) Table 7: Analysis of citric acid in lemon juice via titration with NaOH Trial 1

Trial 2

Trial 3

Volume of NaOH titrated (L)

0.01775

0.01855

0.01735

Moles of NaOH

0.738894371

0.738894371 *

0.738894371

* 0.01775

0.01855

* 0.01735

=0.013115

=0.01371

=0.01282

Moles of Citric Acid

0.013115 / 3 =0.00437

0.01371 / 3 =0.00457

0.01282 / 3 =0.00427

Concentration of citric acid in lemon juice (gram/L)

(192.1214*0. 00437) / 0.025 =33.5828

(192.1214*0.004 (192.1214*0.0 57) / 0.025 0427 / 0.025 =35.11979 =32.8143

Average concentration of citric acid in

(33.5828+35.11979+32.8143) / 3 =33.8389

lemon juice (gram/L) Standard Deviation:

0.958

Concentration of citric acid in commercial

48.0

lemon juice* (gram/L) Error (gram/L)

48-33.5828 =14.4172

12.88021

15.1857

Relative Error (%)

14.4172 / 48 =30

12.88021 / 48 =27

15.1857 / 48 =32

Average Relative error (%)

(30+27+32) / 3 =29.67

* Cite the source of the information for this commercial product

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2637791/ 6. Comment of the accuracy and precision of the analysis of lemon juice. Compared to the previous section of the lab, the precision of the analysis of lemon juice is much more accurate. Although having an average error of roughly 30% isn’t as accurate as we’d like it to be, it’s still moderately accurate. Part of this error is more than likely to be a result of human error throughout the procedure in the lab as well as possible calculation errors/recording errors.

References: ❑ Textbook- section or page number ❑ Blackboard- Chemistry 1000H ❑ Other (specify) -> http://www.endmemo.com/chem/massvolume.php? q=Sodium%20Hydroxide

http://www.endmemo.com/chem/massvolume.php?q=Citric%20Acid...