Question

​50 ml of 0.2 m ammonia solution is treated with 25 ml of 0.2 m hcl. If pkb of ammonia solution is 4.75, the ph of the mixture will be : (1) 3.75 (2) 4.75 (3) 8.25 (4) 9.25 50 ml of 0.2 m ammonia solution is treated with 25 ml of 0.2 m hcl. If pk b of ammonia solution is 4.75, the ph of the mixture will be

Answer 1

Hi,

before solving it, let us go through it once again.

50 ml of 0.2 m ammonia solution is treated with 25 ml of 0.2 m hcl. If pkb of ammonia solution is 4.75, the ph of the mixture will be : (1) 3.75 (2) 4.75 (3) 8.25 (4) 9.25

Moles in each case;

1. for ammonia soln= 50 x 0.2/1000=0.01 moles

2. for Hcl soln = 25 x 0.2/1000= 0.005

Excess moles = 0.01 - 0.005 = 0.005 moles

concentration = 0.005/75= 6.67 x 10^-5 M

pH = -log (6.67 x 10^-5)

    = 4.2