Acid-Base Equilbria

Question 1

Tutorial 12.1

Benzoic acid (C6H5COOH) is a weak acid with pKa 4.22.
Define the term weak acid. [2]

Question 2

Tutorial 12.1 Q1

Benzoic acid (C6H5COOH) is a weak acid with pKa 4.22.
A 0.05 mol dm-3 solution of benzoic acid was prepared.
i. Write the Ka expression for benzoic acid and give its units. [2]
ii. Calculate the pH of the solution. [3]
iii. State two assumptions made when calculating pH in this way. [2]

Question 3

Tutorial 12.1 Q1

Benzoic acid (C6H5COOH) is a weak acid with pKa 4.22.
When benzoic acid solution is diluted by a factor of ten, its pH changes. Describe and explain the change in pH value. [4]

Question 4

Tutorial 12.1 Q1

Benzoic acid (C6H5COOH) is a weak acid with pKa 4.22.
Benzoic acid reacts reversibly with ammonia in solution.
i. Write an equation for this reaction. [1]
ii. Identify the acid-base conjugate pairs in this equilibrium. [2]