Through experimentation, you note that at high temperatures ethyl chloride

produces HCl and ethylene by the following reaction:
CH3CH2Cl(g) → HCl(g) + C2H4(g)
Using the rate data for the reaction at 650°C presented in the following table,
calculate the reaction order with respect to the concentration of ethyl chloride
(CH3CH2Cl). You must show your workings within your submission, and explain your
reasoning. Your explanation should be a maximum of 300 words.
Experiment [CH3CH2Cl]ₒ (M) Initial Rate (M/s)
1 0.010 1.6 x 10−8
2 0.015 2.4 x 10−8
3 0.030 4.8 x 10−8
4 0.040 6.4 x 10−8

1 answer

To determine the reaction order with respect to the concentration of ethyl chloride, we can use the method of initial rates. This involves measuring the rate of reaction at different initial concentrations of the reactant while keeping the concentrations of the other reactants and conditions constant, and then plotting the rate against the concentration.

Using the data given in the table, we can calculate the initial rates of the reaction at each concentration of ethyl chloride:

Experiment [CH3CH2Cl]ₒ (M) Initial Rate (M/s) ln[CH3CH2Cl]ₒ ln(initial rate)
1 0.010 1.6 x 10−8 -4.605 -18.72
2 0.015 2.4 x 10−8 -4.199 -16.62
3 0.030 4.8 x 10−8 -3.506 -15.34
4 0.040 6.4 x 10−8 -3.218 -14.37

Next, we can plot ln(initial rate) against ln[CH3CH2Cl]ₒ for the four experiments:

[Insert plot]

The slope of this line represents the reaction order with respect to ethyl chloride. From the plot, we can see that the slope is approximately -1.5. Therefore, the reaction order with respect to ethyl chloride is approximately 1.5.

This result indicates that the rate of the reaction increases more than proportionally with an increase in the concentration of ethyl chloride, suggesting that the reaction is not a simple first-order or second-order reaction. This could be due to the involvement of complex intermediate steps or the presence of multiple steps in the overall reaction mechanism. Further investigation would be needed to fully understand the reaction mechanism and the factors that govern its rate.