Question

In which case is the number of molecules of water maximum?

• A. $0.00224L$ of water vapours at $1atm$ and $273K$
• B. $18mL$ of water
• C. ${10}^{-3}mol$ of water
• D. $0.18g$ of water

Answer 1

Answer: (B)

$18mL$ of water

The maximum number of water molecules corresponds to the maximum number of moles of water.

$0.00224L$ of water vapours at $1atm$ and $273K$ corresponds to :

$n=\frac{PV}{RT}=\frac{\text{1 atm}\times \text{0.00224 L}}{\text{0.08206 L atm/mol K}\times \text{273 K}}=\text{1.07}\times {10}^{-4}\text{mol}$

$18mL$ of water (density 1 g/mL) corresponds to :

$\text{18 mL}\times \frac{\text{1 g/mL}}{\text{18 g/mol}}=\text{1 mol}$

$0.18g$ of water corresponds to :

$\frac{\text{0.18 g}}{\text{18 g/mol}}=\text{0.01 mol}$

$18mL$ of water has maximum number of moles which corresponds to maximum number of molecules$.

Hence, option $B$ is correct.