# Using experimental results to determine the order of a chemical reaction and the rate constant from your understanding of chemical kinetics and species half life.

A reaction is defined by the following scheme:

X à Y

When the concentration of X in a solution is 1.02 M, the half-life (t1/2) is 160 seconds.

When the concentration of X in solution is 2.05 M, the half-life (t1/2) is 80 seconds.

The above information applies when the reaction takes place at 25 degrees Celsius.

(a) What is the order of the reaction?

(b) Calculate the rate constant for the reaction.

#### Solution Preview

...entration of X. The problem states that the half-life of X decreases by a factor of 2 when the concentration of X is doubled. For this problem, the half-life of X is dependent on the concentration of X, therefore, the reaction is not first order.

To decide whether the reaction is zero order or second order, we will use the values of half-life that were given in the problem, as well as the equations for half-life shown above.

Is the reaction zero order? If the reaction is zero order, the following relation will apply:

(Half-life #1 )/ (Half-life #2) = ({[X]o/2k} for #1)/({[X]o/2k} for #2)

For the ...