Question

Equal volumes of 0.0700 M NH₃ and 0.0350 M HCl are mixed together. What are the concentrations of NH₃ and NH₄ in the reaction?

a) [NH₃] = 0.0525 M, [NH₄] = 0.0175 M
b) [NH₃] = 0.0350 M, [NH₄] = 0.0700 M
c) [NH₃] = 0.0700 M, [NH₄] = 0.0350 M
d) [NH₃] = [NH₄] = 0.0525 M

Answer 1

After mixing equal volumes of 0.0700 M NH₃ and 0.0350 M HCl, the remaining concentration of NH₃ is 0.0350 M (as half of it has reacted), and the concentration of NH₄⁺ formed is also 0.0350 M. Option C is correct.

Step-by-step explanation:

When equal volumes of 0.0700 M NH₃ and 0.0350 M HCl are mixed, a neutralization reaction occurs where NH₃ acts as a base and HCl as an acid:

NH₃ (aq) + HCl (aq) → NH₄⁺ (aq) + Cl⁻ (aq)

Since HCl is the limiting reactant, it will completely react with NH₃. For every mole of HCl, there is one mole of NH₃ that reacts to form NH₄⁺. Initially, there is twice as much NH₃ as there is HCl. After the reaction, the amount of NH₃ that has not reacted will be:

Concentration of NH₃ before reaction - Concentration of HCl = 0.0700 M - 0.0350 M = 0.0350 M NH₃ left

The concentration of NH₄⁺ formed is equal to the original concentration of HCl, which is 0.0350 M since the reaction is 1:1. Therefore, the remaining concentration of NH₃ is 0.0350 M and the concentration of NH₄⁺ is also 0.0350 M. The correct answer is:

c) [NH₃] = 0.0700 M, [NH₄] = 0.0350 M