A 49.06-mL sample of an ammonia solution is analyzed by titration with HCl. The reaction is given below. NH3 (aq) + H + (aq) → NH4 + (aq) It took 39.66 mL of 0.0975 M HCl to titrate (react completely with) the ammonia. What is the concentration of the original ammonia solution?

0.0788 M

Explanation:

NH₃ (aq) + H⁺ (aq) → NH₄⁺ (aq)

Because one mol of ammonia (NH₃) reacts with one mol of HCl, we can use the formula

C₁V₁=C₂V₂

Where V₁ and C₁ are the volume and concentration of the ammonia solution, respectively. While the subscript 2 refers to HCl. We're given V₁, C₂ and V₂; so we solve for C₁:

C₁ = C₂V₂ / V₁ C₁ = 0.0975 M * 39.66mL / 49.06 mL C₁ = 0.0788 M