Question

Equal volumes of 0.030 M NH3 and 0.0150 M HCl are mixed together. What are the concentrations of NH3 and NH4+ in the reaction?

NH₃ (aq) + H⁺ (aq) --> NH₄⁺ (aq)

Answer 1

Solution

Suppose the each equal volume is V.

No. of moles of NH₃ = 0.030 x V = 0.030V

No. of moles of HCl = 0.015 x V = 0.015V

The 0.015V moles of NH₃ are neutralized with 0.015V moles of HCl

= No. of moles of NH₄⁺ = 0.015V moles

Total volume = V + V = 2V

Concentration of ammonium, [NH₄⁺] = No. of moles/ volume

= 0.015V/2V = 0.0075 M (Ans)

Non-reacting no. of moles of NH₃ = (Total No. of moles of NH₃) – (No. of moles of NH₄⁺)

= 0.030V - 0.015V moles = 0.015V moles

Concentration of ammonia, [NH₃] = No. of moles/ volume

= 0.015V/2V = 0.0075 M (Ans)