The radioactive decay constant of 3890 S r is 7.88 × 10-10 s-1. The activity of 15 mg of this isotope will be

Question

The radioactive decay constant of 3890 S r is 7.88 × 10-10 s-1. The activity of 15 mg of this isotope will be (A) 1.5 Ci (B) 2.13 Ci (C) 7.88 Ci (D) 8.76 Ci

Tardigrade Admin · Accepted Answer

Activity λ . N =7.88 × 10-10 × (15 × 10-3/90) × 6.023 × 1023 =7.91 × 10-10 d p s =(7.91 × 1010/3.7 × 1010) =2.13 Ci

Q. The radioactive decay constant of $_{38}^{90} S r$ is $7.88 \times 1 0^{- 10} s^{- 1}$ . The activity of $15 m g$ of this isotope will be

1.5 Ci

2.13 Ci

7.88 Ci

8.76 Ci

Activity $λ . N$
$= 7.88 \times 1 0^{- 10} \times \frac{15 \times 1 0 ^{- 3}}{90} \times 6.023 \times 1 0^{23}$
$= 7.91 \times 1 0^{- 10} d p s$
$= \frac{7.91 \times 1 0 ^{10}}{3.7 \times 1 0 ^{10}}$
$= 2.13 C i$

Q. The radioactive decay constant of 3890​Sr is 7.88×10−10s−1. The activity of 15mg of this isotope will be