Rates of Reactions: Problems and solutions

1.In an experiment involving the reaction, N2 + 3 H2 -----> 2 NH3, the rate was measured as Δ[NH3]Δt = 2.0 × 10-4 mol L-1s-1. What is the rate expressed in terms of (a) -Δ[N2]/Δt and (b) -Δ[H2]/Δt?

Answer 

Ans. (a) 1.0 × 10-4 M s, (b) 3.0 × 10-4 M s-1

2. The reaction, H2(g) + Br2(g) -----> 2 HBr(g) has a rate given by the rate law, Rate = k [H2][Br2]1/2. (a) What are the units of the rate constant k? (b) If the volume of the gas mixture is halved, by what factor is the rate changed?

Answer  (a) (mol/L)-1/2s-1, (b) 2.8