The freezing point of 0.18 M solution of weak acid HA is 272.38 K . The molality of solution is 0.3 M . Find the pH of solution on adding 0.36 M NaA ( K f for water = 1.86 K kg / mol ) (Normal melti

Question

The freezing point of 0.18 M solution of weak acid HA is 272.38 K . The molality of solution is 0.3 M . Find the pH of solution on adding 0.36 M NaA ( K f ​ for water = 1.86 K kg / mol ) (Normal melting point of water = 273 K ) [On addition of salt, there is no charge in volume]

TestHub · Accepted Answer

Δ T f ​ = i × K f ​ × m ​ 0.62 = ( 1 + α ) 1.86 × 0.3 1 + α = 1.86 × 0.3 0.62 ​ = 9 10 ​ α = 9 1 ​ K a ​ pH pH pH ​ = 1 − α C α 2 ​ = 1 − 9 1 ​ ( 0.18 ) ( 9 1 ​ ) 2 ​ = 8/9 0.36 × 81 1 ​ ​ = 5 × 1 0 − 3 = pK a ​ + lo g 0.18 0.36 ​ = 3 − lo g 5 + lo g 2 = 3 − 0.7 + 0.3 = 2.7 ​ ​

Chemistry - Ionic Equilibrium Question with Solution | TestHub

Options:

Doubts & Discussion