What is the ph of a solution that results from mixing together equal volumes of a 0.020 m solution of ammonia and a 0.010 m solution of hydrochloric acid? (pka of nh4 + = 9.25) ?

pH = 9.25

Explanation:

Reaction of ammonia (NH₃) with hydrochloric acid (HCl) is:

NH₃ + HCl → NH₄⁺ + Cl⁻

As equal volumes of a 0.020M solution of NH₃ and a 0.010M solution of react, molarity of NH₃ after reaction is 0.010M and 0.010M of NH₄⁺.

For the buffer NH₄⁺/NH₃ H-H equation to find pH of solution is:

pH = pKa + log₁₀ [NH₃] / [NH₄⁺]

pH = 9.25 + log₁₀ [0.010M] / [0.010M]

pH = 9.25