Question

A first-order reaction has a half-life of 20.0 minutes. Starting with 1.00 x 10^20 molecules

of reactant at time t = 0, how many molecules remain unreacted after 100.0 minutes?
A) 1.00 x 10^4molecules
B) 2.00 x 10^19 molecules
C) 3.20 x 10^16 molecules
D) 5.00 x 10^20 molecules
E) none of the above

Answer 1

E

Step-by-step explanation:

100 minutes is 5 half lives ( 100 min/20 min/half life)

= (1/2 )^5

1 x 10^20 * (1/2)^5 = 3.125 x10^18 molecules