Question

Azomethane decomposes into nitrogen and ethane at elevated temperature: H3C–N=N–CH3 → N2 + C2H6 A chemist studying this reaction at 300°C begins an experiment with an azomethane concentration of 4.52 mM and obtains the following data: Time(s) 100 150 200 250 300 [Azomethane] (mM) 3.50 3.08 2.71 2.39 2.10 Calculate the rate constant. Give an answer with concentration units of molarity and time units of seconds.

Answer 1

Answer:

k = 0,0026 s⁻¹

Explanation:

To calculate the rate constant it is necessary to find out the order of reaction. The R² nearest 1 will be the order of reaction.

For zeroth order the integrated rate law is:

[A] = [A]₀ -kt

The graph of [A] vs t gives a correlation coefficient R² of 0,9944.

The first order is:

ln [A] = ln [A]₀ -kt

The graph of ln [A] vs t gives a R² of 1

The second order is:

1/[A] = 1/[A]₀ -kt

The graph of 1/[A] vs t gives a R² of 0,9942

As R² = 1 for first order, the descomposition of azomethane follows this kinetics order. The lineal correlation is:

y = b - mx

y = 1,5077 - 0,0026x

ln [A] = ln [A]₀ -kt

That means:

-k = - 0,0026 s⁻¹

k = 0,0026 s⁻¹

I hope it helps!