Question

The reaction A → B + C is known to be zero order in A with a rate constant of 5.0 × 10–2 mol/L·s at 25°C. An experiment was run at 25°C where [A]0 = 1.0 × 10–3 M. What is the concentration of B after 5 × 10–3 sec?
A. 5.0 × 10–4 M

B. 7.5 × 10–4 M

C. 5.0 × 10–5 M

D. 2.5 × 10–4 M

E. None of these choices are correct.

Answer 1

Answer:

D. 2.5 × 10–4 M

Explanation:

Data given in the question are;

rate constant of 5.0 × 10–2 mol/L·s

[A]0 = 1.0 × 10–3 M

5 × 10–3 sec

It was mentioned that the reaction is a zero order reaction. One interesting charaacteristics about zero order reactio is that the rate of reaction is indepenedent on the concentrations of the reactants.

This means in zero order reactions, we have;

Rate = Rate constant

Rate =  5.0 × 10–2 mol/L·s

What is the concentration of B after 5 × 10–3 sec?

Concentration = Rate * Time

Concentration = 5.0 × 10–2 * 5 × 10–3

Concentration = 2.5 × 10–4 M

Correct option = D