Question

After 20 min, a reactant has decomposed to 85 % of its original concentration. Which order would the reaction need to be to allow you to solve for the rate constant, k , with only this information?

Answer 1

Answer : The value of rate constant is, $0.0949\text{ min}^{-1}$

Explanation :

First we have to calculate the rate constant, we use the formula :

Expression for rate law for first order kinetics is given by:

$k=\frac{2.303}{t}\log\frac{a}{a-x}$

where,

k = rate constant  = ?

t = time passed by the sample  = 20 min

a = let initial amount of the reactant  = 100 g

a - x = amount left after decay process = 100 - 85 = 15 g

Now put all the given values in above equation, we get

$k=\frac{2.303}{20}\log\frac{100}{15}$

$k=0.0949\text{ min}^{-1}$

Therefore, the value of rate constant is, $0.0949\text{ min}^{-1}$