Question

What fraction of a 100 g sample of K - 42 will remain after 24.8 hours?

Answer 1

1/4

Step-by-step explanation:

From the question given above, the following data were:

Original amount (N₀) = 100 g

Time (t) = 24.8 h

Fraction remaining =?

NOTE: The half-life of K–42 is 12.4 h

Next, we shall determine the number of half-lives that has elapse. This can be obtained as follow:

Time (t) = 24.8 h

Half-life (t½) = 12.4 h

Number of half-lives (n) =?

n = t / t½

n = 24.8 / 12.4

n = 2

Finally, we shall determine the fraction remaining. This can be obtained as follow:

Number of half-lives (n) = 2

Fraction remaining =?

Fraction remaining = 1/2ⁿ

Fraction remaining = 1/2²

Fraction remaining = 1/4