NTA Abhyas JEE Main2020ChemistryIonic EquilibriumPractice
A salt is formed when a weak acid of dissociation constant 1 0 - 4 and weak base of dissociation constant 1 0 - 5 are mixed. The pH and degree of hydrolysis of salt solution are
Options
- A5, 1%
- B7, 14%
- C6.5, 0.3%
- D0.3, 6.5%
Correct answer
C. 6.5, 0.3%
Step-by-step solution
K a = 1 0 - 4 ; p K a = 4 K b = 1 0 - 5 ; p K b = 5 h = K h = K w K a × K b = 1 0 - 14 1 0 - 5 × 1 0 - 5 = 10 × 1 0 - 6 = 3 × 1 0 - 3 % Hydrolysis = h × 100 = 3 × 0.001 × 100 = 0.3 % p H = 7 + 1 2 p K a - 1 2 p K b = 7 + 2 - 2.5 = 6.5