The reaction A → B + C is known to be zero order in A with a rate constant of 4.8 × 10^-2 mol/L • s at 25° C. An experiment was run at 25°C where [A]₀ = 2.0M. What is the concentration of B after 4.0s?

Question

Quizplus · Accepted Answer

The rate law for this reaction is:

rate = k[A]0[B]1[C]1 = k[B][C]

Since the reaction is zero order in A, [A] = [A]0 = 2.0 M throughout the reaction.

At t = 0, [B] = [C] = 0.

After 4.0 s, we can use the integrated rate law for zero-order reactions:

[A] = [A]0 - kt

2.0 M = 2.0 M - (4.8 × 10-2 mol/L • s)(4.0 s)

k[B][C] = 2.0 M

[B] = 2.0 M / [C]

Substituting for [C], we have:

k[B]2.0 M / (k[B]) = 2.0 M

Solving for [B], we get:

[B] = 1.9 × 10-1 M

Therefore, the correct answer is D.

The Reaction a → B + C Is Known to Be