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VOLUME ADDED (mL) pH 0.00 1.96 2.00 2.22 4.00 2.46 7.00 2.77 10.00 3.06 12.00 3.

ID: 493936 • Letter: V

Question

VOLUME ADDED (mL) pH

0.00 1.96

2.00 2.22

4.00 2.46

7.00 2.77

10.00 3.06

12.00 3.29

14.00 3.60

16.00 4.26

17.00 11.08

18.00 11.67

20.00 12.05

25.00 12.40

Complete the following table and show the calculations for the determinations for Trial 1 (see Report Sheet) Record all calculated data the correct number of significant figures. For Trials 2 and 3, the molar mass of the weak acid was determined to be 123 g/mol and 121 g/mol respectively. What is the average molar mass of the weak acid? What are the standard deviation and the relative standard deviation (%RSD) for the molar mass data of the weak acid?

Explanation / Answer

4. Burette reading at stoichiometric point = 16.5 mL

5. Volume of NaOh to reach stoichiometric point = 16.5 mL

7. Moles of NaOH to stoichiometric point = 0.15 Mol * 16.5 mL/1000mL = 2.48*10^-3 mol

8. moles of acid = 2.48*10^-3 mol

9. Molar mass of acid = 0.297gm/ 2.48*10^-3 mol =119.76gm/mol

10. Volume of NaOH halfway = 16.5/2 = 8.25

11.at halfway point pH = pKa = 2.9