Question

A hydrochloric (HCl) solution has a molar concentration of 0.0045 M, calculate the [H3O+] , [OH-] and pH of the solution.

Answer 1

1) [H₃O⁺] = {HCl] = 0.0045 M.

2) [OH⁻] = 2.22 x 10⁻¹² M.

3) pH = 2.346.

Step-by-step explanation:

HCl is completely dissociated yo its ions in solution:

HCl + H₂O → H₃O⁺ + Cl⁻,

1) [H₃O⁺] = {HCl] = 0.0045 M.

2) [OH⁻]:

∵ [H₃O⁺][OH⁻] = 10⁻¹⁴.

∴ [OH⁻] = 10⁻¹⁴/[H₃O⁺] = 10⁻¹⁴/(0.0045 M) = 2.22 x 10⁻¹² M.

3) pH:

For strong acids like HCl:

pH = - log[HCl] = - log[0.0045 M] = 2.346.