Question

Acetone reacts with iodine in the presence of hydrochloric acid and starch indicator in accordance with the rate law below:

Rate = k [CH₃COCH₃]^x [I₂]^y [H⁺]^z

Based on the experimental data, determine the reaction order in respect to acetone (CH₃COCH₃), iodine (I₂), and hydrochloric acid (H⁺). Make sure to round the values of x, y, and z to the nearest whole number. List your answers separated by commas.

Mixture	Initial Concentration (M)			Rate = - delta[I2]/delta t (change of conc. of iodine vs. change of time)
	Acetone, CH3COCH3	Iodine, I2	Hydrochloric acid, H+
1	0.50	3.8 x 10-4	6.3 x 10-2	1.31 x 10-6
2	0.50	2.5 x 10-4	6.3 x 10-2	1.28 x 10-6
3	0.50	2.5 x 10-4	1.2 x 10-1	2.55 x 10-6
4	1.0	2.5 x 10-4	6.3 x 10-2	3.25 x 10-6

Using the lab data for any of the four mixtures of your choice, determine the value of the rate constant, k. Make sure to provide the correct units of measurements.

Answer 1

The reaction rate is given by:

Substituting in this equation the values ​​of the concentrations and rats of mixtures 1 and 2, we have:

For the 1 mixture:

For the 2 mixture:

Dividing both equations we have:

Taking logarithm on both sides of the equation and clearing the y we obtain the order of reaction with respect to I₂:

In a similar way for mixtures 2 and 3, the reaction order with respect to H⁺ is obtained

In a similar way for mixtures 2 and 4, the reaction order with respect to CH₃COCH₃ is obtained

Therefore, it is concluded that the reaction orders are:

x = 1

y = 0

z = 1

Clearing k from the reaction rat you have:

Substituting in the previous equation considering y = 0, zero order for the I₂ we have:

With the data of the mixture 4

The constant is

k = 5.1587x10^-5 1/M³s