Cesium-134 is a $\beta$ emitter with a half-life of 2.0 years. How much of a 2.50-g sample of cesium-134 will remain after 10 years?
A) 0.0024 g
B) 0.078 g
C) 0.25 g
D) 0.50 g
E) None of these choices is correct.

Question

Quizplus · Accepted Answer

After 2.0 years (one half-life), half of the original sample will remain: 2.50 g / 2 = 1.25 g. After another 2.0 years, half of that remaining sample will decay: 1.25 g / 2 = 0.625 g. Repeat for a total of 5 half-lives (10 years / 2 years per half-life), and the amount remaining is:
2.50 g / 2^5 = 2.50 g / 32 = 0.078 g (rounded to three significant figures). Therefore, the answer is B.

Cesium-134 Is A β\betaβ Emitter with a Half-Life of 2

Cesium-134 Is A $\beta$ Emitter with a Half-Life of 2