Question

The pressure of sodium vapour in a $1.0L$ container is $10$ torr at ${1000}^{0}C$. How many atoms are present in the container?

• A. $9.7\times {10}^{17}$
• B. $7.6\times {10}^{19}$
• C. $4.2\times {10}^{17}$
• D. $9.7\times {10}^{19}$

Answer 1

The correct option is B $7.6\times {10}^{19}$

$10$ torr = $0.0013\times 10$ atm = $0.013$ atm

By ideal gas equation,

$n=\frac{PV}{RT}=\frac{0.013\times 1}{0.0821\times 1273}=1.24\times {10}^{-4}$ moles

$\therefore$ Number of atoms = $1.24\times {10}^{-4}\times 6.022\times {10}^{23}$ = $7.6\times {10}^{19}$ atoms

Hence, option B is correct.