Ethyl chloride vapor decomposes by the first-order reaction:

C2H5Cl â C2H4 + HCl
The activation energy is 249 kJ/mol and the frequency factor is 1.60 Ã 1014 s^â1.

a. Find the value of the specific rate constant at 876 K.
b. Find the fraction of the ethyl chloride that decomposes in 20 minutes at this temperature.

Respuesta :

Explanation:

(a)  The given data is as follows.

            Frequency factor A = [tex]1.60 \times 10^{14} s^{-1}[/tex]

           Activation energy ([tex]E_{a}[/tex]) = 249 kJ/mol

           Gas constant = 8.314 J/mol K

            Temperature (T) = 876 K

Hence, calculate the specific rate constant as follows.

                  K = [tex]Ae^{\frac{-E_{a}}{RT}}[/tex]

                      = [tex]1.60 \times 10^{14} s^{-1} e^{\frac{249000 J/mol}{8.314 J/mol K \times 876 K}}[/tex]

                      = [tex]1.60 \times 10^{14} s^{-1} \times 1.034[/tex]

                      = [tex]1.128 \times 10^{29}[/tex]

Hence, the value of specific rate constant K is [tex]1.6544 \times 10^{14}[/tex].

(b)  It is given that time is 20 minutes. As there are 60 seconds present in 1 min. Therefore, seconds present in 20 minutes are as follows.

            [tex]20 min \times \frac{60 sec}{1 min}[/tex]

            = 1200 sec

Hence, for the first order reaction the fraction remaining is as follows.

                [tex]\frac{C}{C_{o}} = e^{-kt}[/tex]

                              = [tex]e^{-1.6544 \times 10^{14} \times 1200 sec}[/tex]

                              = 0

Hence, fraction decomposed = 1 - 0 = 1

Therefore, the fraction of the ethyl chloride that decomposes in 20 minutes at this temperature is 1.

The rate constant of the first order reaction is 0.227.

What is a first order reaction?

A first order reaction is that in which the rate of reaction depends on the concentration of one reactant.

Using the Arrhenius equation;

k=A e^-Ea/RT

k = rate constant

A = frequency factor

Ea = activation energy

R = gas constant

T = temperature

k = 1.60 * 10^14e^-249 * 10^3/8.314 * 876

k =0.227

We know that;

N=Noe^-kt

Where;

N = amount ptresent at time t

No = amount initially present

k = rate constant

t = time

N/No =e^-kt

N/No =e^-(0.227 * 20 * 60)

= 0

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