2H2 (g) + 2NO (g) →2H2O (g) + N2 (g) Part A If the concentration of NO changed from 0.100 M to 0.025 M in the first 15 minutes of the reaction, what is the average rate of the reaction during this time interval?

0.0025 M/min

Explanation:

The rate of a reaction can be calculated for an element, based on its stoichiometric coefficient. For a reaction:

aA + bB = cC + dD, the rate will be

r = - (1/a) x (Δ[A]/Δt) = - (1/b) x (Δ[B]/Δt) = (1/c) x (Δ[C]/Δt) = (1/d) x (Δ[D]/Δt)

Where Δ[X] is the variation of the concentration of the X compound, Δt is the time variation, and the signal of minus in the reagents compounds is because they are disappearing, so Δ[X] will be negative, and r must be positive. So, for the reaction given:

r = - (1/2) x (Δ[NO]/Δt)

r = - (1/2) x ((0.025 - 0.1) / 15)

r = 0.0025 M/min