13 Which of the following solutions will have a pH of 30 a 1

13. Which of the following solutions will have a pH of 3.0? (a) 1.0 × 10-3 M CH3COOH (b) 1.0 × 10-3 M NH3 (c) 1.0 × 10-3 M NH (d) 1.0 × 10-3 M HI (e) Both (b) and (c)

Solution

Answer option D) 1.0 * 10^-3 M of HI

HI is strong acid so all HI molecules would be ionized. Hence concentration of H+ ions also 1.0 * 10^-3 M

pH = - log (1.0 * 10^-3) => 3.0

Remaining all are weak acid hence dissociation into ions will not be 100 % . So concentration of H+ ions would be less than 1.0 * 10 ^-3 M. Therefore pH would be greater than 3.0