Question

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

• A. more than 20 minutes
• B. less than 20 minutes
• C. equal to the 20 minutes
• D. Infinity

Answer 1

The correct option is C equal to the 20 minutes

In 20 minutes the concentration decreases from 1.0 M to 0.6 M.
This corresponds to 40% decrease in the concentration.
Again, the concentration decreases from 0.6 M to 0.36 M.
This is also 40% decrease.
Hence it will take same time i.e 20 minutes.