Question

The half-life of sr-90 is 28 years. after 56 years of decay only 0. 40 g of a sample remains. what was the mass of the original sample?
a. 0. 050 g
b. 0. 10 g
c. 3. 2 g
d. 1. 6 g

Answer 1

Half-life is the time taken for the concentration of the substance to reduce by 50%. The original sample of strontium had a mass of 1.6 gms. Thus, option d is correct.

What is half-life?

The half-life of any radioactive substance is the time period at which the concentration will get reduced to half the initial amount. The initial mass of Sr-90 is calculated as,

$N(t) = N_{0} (\dfrac{1}{2})^{ \frac{t }{t 1/2}}$

Given,

Quantity of the remaining substance N (t) = 0.40 gm

Initial radioactive substance quantity $N_{0}$ =?

Time duration (t) = 56 years

Half-life = 28 years

Substituting values above:

$\begin{aligned} 0.40 &= N_{0} (\dfrac{1}{2}) ^{{\frac{56}{28}}\\\\0.40 &= N_{0} (\dfrac{1}{2})^{2}\end{aligned}$

= 1.6 gm

Therefore, option d. the initial mass of Sr is 1.6 gm.

Learn more about half-life here:

brainly.com/question/16145921

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