Equal volumes of 0.0400 M NH₃ and 0.0200 M HCl are mixed together. What are the concentrations of NH₃ and NH₄ in the reaction?
a) [NH₃] = 0.0200 M, [NH₄] = 0.0200 M
b) [NH₃] = 0.0200 M, [NH₄] = 0.0400 M
c) [NH₃] = 0.0300 M, [NH₄] = 0.0300 M
d) [NH₃] = 0.0300 M, [NH₄] = 0.0200 M