Question

The maximum number of molecules are present in:

• A. $36$ g $H_{2}O$
• B. $28$ g $CO$
• C. $46$ g $C_2{H}_{5}OH$
• D. $54$ g $N_2{O}_5$

Answer 1

The correct option is A $36$ g $H_{2}O$

Number of molecules = Number of moles $\times N_A$

$=\frac{\text{given mass}}{\text{molar mass}}\times N_A$

The more the number of moles, the more will be the number of molecules.

$36$ g of water($H_{2}O$) corresponds to $\frac{36}{18}=2$ moles (Molar mass 18 $gmo{l}^{-1}$).

$28$ g of $CO$ corresponds to $\frac{28}{28}=1$ mole (Molar mass 28 $gmo{l}^{-1}$).

$46$ g ethanol($C_2{H}_{5}OH$) corresponds to $\frac{46}{46}=1$ mole (Molar mass 46 $gmo{l}^{-1}$).

$54$ g dinitrogen pentoxide($N_2{O}_5$) corresponds to $\frac{54}{108}=0.5$ moles (Molar mass 108 $gmo{l}^{-1}$).

Hence, option A is correct.