If 40 g of substance of half-life 5.0 hours remain from an original sample of 1.28 kg, the time that has passed is
A) 1.0 hour.
B) 20 hours.
C) 25 hours.
D) 80 hours.
E) 160 hours.

Question

Quizplus · Accepted Answer

The half-life formula is used to determine the time passed: N = N0 * (1/2)^(t/T), where N is the remaining amount, N0 is the initial amount, t is the time passed, and T is the half-life. Solving for t when N = 40 g, N0 = 1280 g, and T = 5 hours gives t = 25 hours.

If 40 G of Substance of Half-Life 5