The following questions refer to the gas phase decomposition of ethylene chlorid

Question

The following questions refer to the gas phase decomposition of ethylene chloride

C2H5Cl products

Experiment shows that the decomposition is first order. The following data show kinetics

information for this reaction.

Time (s)               1.0       2.0

ln [C2H5Cl] (M)    -1.625    -1.735

What is the rate constant for this decomposition if [C2H5Cl] is 0.20M?

What was the initial concentration of the ethylene chloride? K=0.12

What would the concentration be after 4.0 seconds? based on previous question

Explanation / Answer

To calculate the rate constant use the following expression:

ln [A] - In[A]o = - k t

here, ln [C2H5Cl] (M) at t means 1 sec    = -1.625

[C2H5Cl] 0 (M)   = 0.20 M

Time, t = 1.0 s

Then;

-1.625 – In 0.20 = - k *1 s

-1.625- (1.61)= - k s

- 0.015 = -k s

k = 0.015 s-1

To calculate the initial concentration use the following expression:

ln [A] - In[A]o = - k t

here, ln [C2H5Cl] (M) at t means 1 sec    = -1.625

[C2H5Cl] 0 (M)   = ? M

Time, t = 1.0 s

K = 0.12

Then;

-1.625 – In [A]o = - 0.12 *1 s

– In [A]o = 1.505

[A]o = e^-1.505

[A]o = 0.22 M

To calculate the concentration after 4 sec use the following expression:

ln [A] - In[A]o = - k t

here, [C2H5Cl]0 (M)    = 0.22 M

[C2H5Cl] t (M)   = ? M at 4 sec

Time, t = 4.0 s

K = 0.12

Then;

In[A] – In (0.22)= - 0.12* 4

In[A]-(-1.51) = -0.48

In[A] +1.51 = -0.48

In[A] = -1.99

[A] = e^-1.99

[A] = 0.136 M

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