Question

This problem is 1st order for half life.

How long would it take for the concentration of cyclopropane to decrease to 50% of its initial value? to 25% of its initial value?

Rate constant is 9.2/s

I set up like this...

t1/2= 0.693/9.2/s= 0.075s at 50%

I can't figure out how to get the answer of 0.151s from 25%...

Answer 1

if it reduces to 1/2 in .075s, it will reduce to 1/4 in twice that, or .151s.

The half-life is 0.075s, so since 1/4 = 2(1/2), it takes 2 half-lives to fall to 25%.