Question

An $\alpha$-particle change into a Helium into a Helium atom. In the course of one year the volume of Helium collected from a simple of Radium was found to be ${1.12\times 10}^{-2}mL$ at STP. The number of $\alpha$particles emitted by the sample of Radium in the same time is:

• A. ${6\times 10}^{17}$
• B. ${3\times 10}^{17}$
• C. ${1.5\times 10}^{17}$
• D. ${1.2\times 10}^{17}$

Answer 1

The correct option is B ${3\times 10}^{17}$

$\alpha$ particles are charged helium nuclear which give helium atoms in a $1:1$ ratio.

22.4 L helium$⟶6.023\times {10}^{23}$ particles

$\therefore 1.12\times {10}^{-5}L$ helium has $x$ particles

$x=\frac{6.023\times {10}^{23}\times 1.12\times {10}^{-5}}{22.4}=3.012\times {10}^{17}$

Hence, the correct option is $B$