Question

How many $O_2$ molecules are present in $2.0$ L of oxygen gas at ${27}^{o}C$ temperature and $3.0$ atm pressure?

• A. $1.0\times {10}^{23}$
• B. $1.5\times {10}^{23}$
• C. $1.5\times {10}^{24}$
• D. $2.5\times {10}^{24}$

Answer 1

Answer: (B)

$1.5\times {10}^{23}$

$PV=nRT$

$3\times 2=n\times 0.0821\times 300$

No. of $O_2$ molecules $n=\frac{2}{8.21}\times 6.022\times {10}^{23}$

$=14.6\times {10}^{23}$

$=1.5\times {10}^{23}$

Ans (B)