Calculate the pH of a Solution at Each Temperature

Question

Calculate the pH of a 0.0242 M KOH solution at each temperature.

T (°C)K_w

At 5°C _ K_w = 1.88 x 10^–15

At 45°C _ K_w = 3.94 x 10^–14

5°C pH=

45°C pH=

Answer 1

0.0242 M KOH ==> 0.0242 M K⁺ + 0.0242 M OH^-

@5ºC Kw = 1.88x10^-15 = [H⁺][OH^-]

1.88x10^-15 = [H⁺][0.0242]

[H⁺] = 7.77x10^-14

pH = -log [H+] = -log 7.77x10^-14

pH = 13.1

@45ºC Kw = 3.94x10^-14 = [H⁺][OH^-]

3.94x10^-14 = [H⁺][0.0242]

[H⁺] = 1.63x10^-12

pH = -log [H⁺] = -log 1.63x10^-12

pH = 11.8