# In the first world war ,$1.1\times 10^8$kg of position gas were fired on the allied forces.If the gas is assumed to be phosgene,how many molecules of the gas correspond to the amount fired on allied forces.

$\begin{array}{1 1}(a)\;1.9\times 10^{-15}&(b)\;6.7\times 10^{32}\\(c)\;2.9\times 10^{-15}&(d)\;6.7\times 10^{29}\end{array}$

Phosgene is $COCl_2$(mol.wt =99)
$99g$=Nmolecules
$\therefore 1.1\times 10^{11}g=\large\frac{N\times 1.1\times 10^{11}}{99}$
$\Rightarrow 6.7\times 10^{32}$
Hence (b) is the correct answer.