Question

1 L of a gas is at a pressure of ${10}^{-6}$ of $Hg$ at ${25}^{\circ }C$. How many molecules are present in the vessel?

• A. $3.2\times {10}^6$
• B. $3.2\times {10}^{13}$
• C. $3.2\times {10}^{10}$
• D. $3\times {10}^4$

Answer 1

Answer: (B)

$3.2\times {10}^{13}$

$\frac{{\rho }_1{V}_1}{T_1}=\frac{{\rho }_2{V}_2}{T_2}$
$\Rightarrow \frac{{10}^{-6}\times 1000}{298}=\frac{760\times V_2}{273}$
$V_2=1.2\times {10}^{-6}cc\left(atSTP\right)$
No. of molecules $=\frac{6.02\times {10}^{23}}{22400}\times 1.2\times {10}^{-6}$
$=3.2\times {10}^{13}$