Question

The concentration of ethanol in a patient’s blood was monitored over time. Plot the following data in three ways to determine the reaction order and the rate constant.

Time (h)	[CH3CH2OH] (mM)
0.00	1.000
1.00	0.894
2.00	0.799
3.00	0.714
4.00	0.638
5.00	0.571
6.00	0.510
7.00	0.456
8.00	0.408
9.00	0.364
10.00	0.326

Answer 1

Let the rate of the reaction be zero order

[Ao] - [At] = kt

1.000 - 0.894 = k(1)

k = 0.106 Ms^(-1)

[Ao] - [At] = kt

1.000 - 0.799 = k(2)

k = 0.1005 Ms^(-1)

Hence the reaction is not zero order

Let the reaction be first order

ln(Ao/At) = kt

ln(1/0.894) = kt

k = ln(1.1185) = 0.04866 s^(-1)

ln(1/0.799) = k(2)

k = ln(1.25156)/2 = 0.0487 s^(-1)

Hence the reaction is first order wrt reactant with the rate constant equal to 0.0487 s^(-1)

Plotting the data, it will be done for ln[A] wrt t, since it will give the straight line graph