Question

The number of molecules in $1\text{kg}$ of nitrogen gas sample (molar mass = 28 g/mol) is approximately:

• A. $2.15\times {10}^{25}$
• B. $3.6\times {10}^{23}$
• C. $8.06\times {10}^{23}$
• D. $4.08\times {10}^{22}$

Answer 1

The correct option is A $2.15\times {10}^{25}$

1 mole of nitrogen or $28\text{g}$ of nitrogen contains $6.023\times {10}^{23}$ molecules of nitrogen.
Thus, $28\text{g}$ of nitrogen contain molecules = $6.023\times {10}^{23}$
$1000\text{g}$ of oxygen contain molecules $\frac{6.023\times {10}^{23}}{28}\times 1000$
$=2.15\times {10}^{25}$molecules