A substance undergoes a first-order decomposition. After 40.0 min at 500 degrees C, only 12.5% of the original sample remains. What is the half-life of the decomposition? If the original sample weighted 243 g, how much would remain after 2 hours?

Question

A substance undergoes a first-order decomposition.  After 40.0 min at 500 degrees C, only 12.5% of the original sample remains.  What is the half-life of the decomposition? If the original sample weighted 243 g, how much would remain after 2 hours?

College Hacker · Accepted Answer

n * t1/2 = mass/(2^n) n * t1/2 = 2 hrs = 120 mins n = 120/13.3 n = 9.02 (n = number of half-cycles) remaining mass = 243/(2^9.02) = 0.467g 0.467g is remaining after 2 hrs

College Hacker · Answer

).5^n = 0.125 n = 3 t 1/2 = 40 mins / 3 t 1/2 = 13.3 mins Hope that helps

Writeacher · Answer

Is Bob going to trust someone who calls himself "College Hacker"? Hmmm!

College Hacker · Answer

It's up to Bob. If you find anything wrong with the solution, please correct it :)