Question

In a first order decomposition reaction, 50% of a compound decomposes in 10.5 min. How long will it takes for 75% of the compound to deomposses?

Answer 1

what you've just been told is the half-life of the reaction. "normal" chemical reactions have half-lives just like nuclear decays have half-lives. If 50% of the reaction occurs in 10.5min, the half-life is 10.5min. In the next half-life, 50% of the remaining 50% will react, leaving behind 25% of what you started with. At this point, 25% remains, so 75% must have decomposed, over 2 half-lives, or 21 minutes.

Answer 2

ok...i got it...thanks