Question

A student titrated 0.180 g of an unknown acid with 0.10 M NaOH solution and the follow data set was obtained: mL of 0.1M NAOH mL of 0.1M pH pH NaOH 0 2.20 20 6.32 22 2 3.25 6.70 4 4.00 4.25 24 7.00 26 6 9.00 8 11.20 4.50 28 10 4.81 30 11.70 12 5.25 32 12.00 5.55 14 34 12.22 16 5.75 36 38 12.40 18 6.10 12.60 1. Prepare a titration curve using Microsoft Excel. See Appendix C for directions on graphing. 2. Is this acid monoprotic or diprotic? Briefly explain. 3. Is this acid strong or weak? Briefly explain. 4. Determine the molar mass of the unknown acid 5. Determine the pKa(s) of the acid. 6. Identify the acid using the table on the previous page

please ignore question1

Answer 1

Question 2.

The acid is diprotic.

Explanation: There are two raises, one at pH 9, the other at pH 11.2

Question 3.

The acid is weak.

Explanation: At pH 9 (> 7), the acid reached the first-equivalence point.

Question 4.

The MW of the acid is 69.231 g/mol

Explanation: The moles of acid = The moles of acid at the first-equivalence point = (26/1000) L * 0.1 mol/L = 0.0026 mol

i.e. The molar mass of the acid = 0.18 g/0.0026 mol = 69.231 g/mol