Question

Oxygen is present in a litre flask at a pressure of $7.6\times {10}^{-10}g$mm of Hg. The number of oxygen moleculesin the flask at $0^{o}C$ is :

• A. $2.7\times {10}^{9}molecules$
• B. $2.7\times {10}^{10}molecules$
• C. $2.7\times {10}^{11}molecules$
• D. $2.7\times {10}^{12}molecules$

Answer 1

The correct option is B $2.7\times {10}^{10}molecules$

The number of oxygen molecules in the flask
$\frac{PV{N}_A}{RT}=\frac{7.6\times {10}^{-10}\times 1\times 6.023\times {10}^{23}}{760\times 0.0821\times 273}=2.7\times {10}^{10}$ molecules.