exam 2 buffer questions

# exam 2 buffer questions - Past buffer and titration...

This preview shows pages 1–2. Sign up to view the full content.

Past buffer and titration questions from Sp08 Exam II: 1. Which of the following combinations would be the best to buffer an aqueous solution at a pH of 5.0? (a) H 3 PO 4 and H 2 PO 4 K a1 = 7.5 10 3 (b) HNO 2 and NO 2 K a = 4.5 10 4 (c) CH 3 CO 2 H and CH 3 COO K a = 1.8 10 5 (d) H 2 PO 4 and HPO 4 2 K a2 = 6.2 10 8 (e) NH 4 + and NH 3 K a = 5.7 10 10 2. If you wanted to make a 3 liter solution of 500 mM formic acid buffer at pH 3.9, how many grams each of sodium formate (MW = 68.0 g/mol) and formic acid (MW = 46.0 g/mol) would you add? (See Table for K a values). (a) 98.6 g sodium formate & 2.3 g formic acid (b) 13.8 g sodium formate & 13.6 g formic acid (c) 20.2 g sodium formate & 9.4 g formic acid (d) 41.5 g sodium formate & 40.9 g formic acid (e) 60.5 g sodium formate & 28.1 g formic acid 3. What is the pH of a solution containing 0.20 M benzoic acid (HC 7 H 5 O 2 ) and 0.35 M sodium benzoate (NaC 7 H 5 O 2 )? The pK a of benzoic acid is 4.19.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## exam 2 buffer questions - Past buffer and titration...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online