Question

For first order reaction the concentration of reactant decreases from 0.2 to 0.1 M in 100 minutes. What is the rate constant of the reaction?

Options

• 144.3 min^-1

• 69.3 min^-1

• 6.93 × 10^-3 min^-1

• 6.93 min^-1

Answer 1

6.93 × 10^-3 min^-1 

Explanation:

Given,

Time (t) = 100 min

[A₀] = 0.2 M

[A] = 0.1 M

According first order reaction,

rate constant (k) = `2.303/"t" log  (["A"_0])/(["A"])`

`= 2.303/(100  "min") log  ([0.2])/([0.1])`

`= 2.303/(100  "min") xx 0.3010` [∵ log 2 = 0.3010]

= 6.93 × 10^-3 min^-1