Question

The number of chlorine atoms in $ 20\,mL$ of chlorine gas at STP is _____$10^{21} $. (Round off to the Nearest Integer). [Assume chlorine is an ideal gas at STP $R =0.083 \,L \text { bar } mol ^{-1} K ^{-1}, N _{ A }=6.023 \times 10^{23}$

Answer 1

$PV = nRT $

$1.0 \times \frac{20}{1000}=\frac{ N }{6.023 \times 10^{23}} \times 0.083 \times 273$

$\therefore $ Number of $Cl _{2}$ molecules, $N =5.3 \times 10^{20 }$

Hence, Number of $Cl$-atoms $=1.06 \times 10^{21}$

$\approx 1 \times 10^{21}$