Question

The number of molecules in $1c{m}^3$ of an ideal gas at $0^{o}C0$ and at a pressure of ${10}^{-5}$mm of mercury is-

• A. $2.7\times {10}^{19}$
• B. $3.5\times {10}^{11}$
• C. $6.0\times {10}^{23}$
• D. $6\times {10}^{12}$

Answer 1

The correct option is A $2.7\times {10}^{19}$

$1$ molof any gas at NTP occupies volume of $22400c{m}^3$

Volume of $6.022\times {10}^{23}$ molecules of gas $=22400c{m}^3$

Number of molecules in $1$cm of volume $=\frac{1c{m}^3\times 6.022\times {10}^{23}molecules}{22400c{m}^3}$

$=2.7\times {10}^{19}$ molecules.

Hence, the answer is $2.7\times {10}^{19}$ molecules.