Formula For Salts of Strong Acids and Weak Bases

Sep 06, 2022, 16:45 IST

Salts of strong acids and weak bases [SA-SB]

Such salts give acidic solutions in water. Some of such salts are : NH₄Cl, ZnCl₂, FeCl₃ etc. For the purpose of discussion, we will consider hydrolysis of NH₄Cl. For More Chemistry Formulas just check out main pahe of Chemsitry Formulas. 

When NH₄ Cl is put in water, it completely ionises in water to give NH₄⁺ and Cl^- ions. NH₄⁺ ions combine with OH^- ions furnished by weakly dissociated water to form NH₄OH (weak base). Now for keeping K_w constant, water further ionises to give H⁺ and OH^- ions, where OH^- ions are consumed by NH₄⁺ ions leaving behind H⁺ ions in solution to give an acidic solution. 

pH of solution :

Example For Salts of Strong Acids and Weak Bases

Example 1                  

The basic ionisation constant for hydrazine, N₂H₄ is 9.6× 10^–7. What would be the percent hydrolysis of 0.1 N₂H₅Cl ?

A. 0.016
B. 3.2
C. 1.6
D. 0.032
 

Ans. D

Example 2      

The pH of a 0.02 M aqueous solution of NH₄Cl  is equal to

A. 3.78
B. 4.73
C. 5.48
D. 7.00
 

Ans. A