Question

If the Ka of a monoprotic weak acid is 3.1 × 10-6, what is the pH of a 0.14 M solution of this acid?

Answer 1

pH is calculated by using following formula,

pH = - log [H⁺]

As we are not given with [H⁺], so we will calculate it bu using following formula,

[H⁺] =
`√(Ka . M)`

Putting Values and solving,

[H⁺] =
`√(1.3*10^-6 * 0.17)`

[H⁺] =
`√(2.21*10^-7)`

[H⁺] = 4.70 × 10⁻⁴

Now,
pH = - log (4.70 × 10⁻⁴)

pH = 3.32