Question

A $5\text{L}$ vessel contains $2.8\text{g}$ of $N_2$. When heated to $1800\text{K}$, $30\%$ molecules are dissociated into atoms. The correct statement(s) is/are :

• A. Total no. of moles from all the species present in the container will be 0.13
• B. Total no. of molecules in the container will be close to $0.421\times {10}^{23}$
• C. Total no. of moles in the container will be 0.098
• D. Total no. of molecules in the container will be close to $0.421\times {10}^{22}$

Answer 1

Answer: (A), (B)

The correct options are
A Total no. of moles from all the species present in the container will be 0.13
B Total no. of molecules in the container will be close to $0.421\times {10}^{23}$

(a) and (b) Explanation: $30\%$ of molecule dissociated $N_2\to 2N$
Amount of $N_2$ left $=\frac{2.8}{28}\times \frac{70}{100}=0.1\times 0.7=0.07$ (in moles)
No. of moles of $N$ atoms formed $=2\times \frac{30}{100}\times 0.1=0.06$
(a) Total no. of moles $=0.07+0.06=0.13$
(b) Total number of molecules $=0.07\times 6.023\times {10}^{23}=4.2\times {10}^{22}\text{molecule}=0.421\times {10}^{23}$
$\because$ We have to calculate molecules of nitrogen and not atoms.