Question

A solution of ammonia has a pH of 11.8. What is the concentration of OH– ions in the solution?

Answer 1

pH = 11.8

Using the Formula,

pH = - log[H₃O⁺]

11.8 = - log[H₃O⁺]

log[H₃O⁺] = -11.8

Taking antilog both the sides,

antilog (log[H₃O⁺]) = antilog (-11.8)

∴ [H₃O⁺] = antilog(-11.8)

∴ [H₃O⁺] = 1.58 × 10⁻¹²

[OH-] = 10⁻¹⁴/( 1.58 × 10⁻¹²)

[OH-] = 6.32 × 10⁻³

Hope it helps .