The activity of a sample of radioactive element `X^(100)` is 6.02 curie. Its decay constant is `3.7 xx 10^(-4) s^(-1)`.
The initial mass of the sample will be
a. `10^(-6) g` b. `10^(-8) g` c. `10^(-20) g` d. `10^(-15) g`

Options

A. a. `10^(-6) g`
B. b. `10^(-8) g`
C. c. `10^(-20) g`
D. d. `10^(-15) g`

Answer

d. `10^(-15) g`

Explanation

We know that
Activity `= K xx (W)/("Atomic Weight") xx 6.023 xx 10^(23)`
Given activity `= 6.02` curie or `6.02 xx 3.7 xx 10^(10) s^(-1)`
`:. 6.02 xx 3.7 xx 10^(10) = 3.7 xx 10^(4) xx (W)/(100) xx 6.023 xx 10^(23)`
or `W = 10^(-15) g`