Answer to Question #243475 in Chemistry for deevika

Question

A solution of hydrochloric acid has a concentration of 4.50g L-1 .

 (i) Calculate the hydronium ion concentration in mol L-1 .

(ii) Calculate the pH of the solution.

 

Answer 1

Solution:

hydrochloric acid = HCl

hydronium ion = H₃O⁺

The molar mass of HCl is 36.458 g/mol

Hence,

(4.50 g HCl L^-1) × (1 mol HCl / 36.458 g HCl) = 0.123 mol L^-1

C(HCl) = 0.123 mol L^-1

HCl(aq) + H₂O(l) → H₃O⁺(aq) + Cl^-(aq)

HCl is a strong acid.

Hence,

[H₃O⁺] = C(HCl) = 0.123 mol L^-1

[H₃O⁺] = 0.123 mol L^-1

We can convert between [H₃O⁺] and pH using the following equation:

pH = - log[H₃O⁺]

pH = - log(0.123) = 0.91

pH = 0.91

Answers:

(i): [H₃O⁺] = 0.123 mol L^-1

(ii): pH = 0.91