Question

For a given reaction of first order, it takes $20\text{min}$ for the concentration to drop from $1.0\text{M}$ to $0.6\text{M}$. The time required for the concentration to drop from $0.6\text{M}$ to $0.36\text{M}$ will be:

• A. More than $20\text{min}$
• B. Less than $20\text{min}$
• C. Equal to the $20\text{min}$
• D. Infinity

Answer 1

The correct option is C Equal to the $20\text{min}$

In $20\text{minutes}$ the concentration decreases from $1.0\text{M}$ to $0.6\text{M}$.
This corresponds to $40$% decrease in the concentration.
Again, the concentration decreases from $0.6\text{M}$ to $0.36\text{M}$.
This is also $40$% decrease.
Hence it takes same time i.e $20\text{minutes}$.