Question

The concentration of a reactant in a solution falls from 0.2 M to 0.1 M in 2 hours and to 0.05 M in 4 hours. The order of reaction is:

• A. zero
• B. two
• C. one
• D. half

Answer 1

Answer: (C)

one

We find $0.2⟶0.1M$ takes $t_{1/2}=2hrs$

and $01M⟶0.5M$ takes $t_{1/2}=2hrs$

thus $t_{1/2}$ is a constant which implies

$t_{1/2}=\frac{ln\left(2\right)}{k}⟶$ First order half life.