Question

The number of atoms in $1\text{mL}$ of ammonia gas at STP is:

• A. $2.7\times {10}^{19}$
• B. $1.08\times {10}^{20}$
• C. $10.8\times {10}^{20}$
• D. $5.4\times {10}^{19}$

Answer 1

The correct option is B $1.08\times {10}^{20}$

1 molecule of ammonia has 4 atoms $(1N+3H)$.
$22400\text{mL}$ of volume is occupied by 1 mole of gas or $4\times N_A$ atoms.
Then, $1\text{mL}$ of volume is occupied by $=\frac{4\times N_A}{22400}=1.08\times {10}^{20}$ atoms.