Chemistry - Mole Concept Question with Solution | TestHub

The number of molecules is directly proportional to the number of moles.

Number of moles $n=\frac{\text{Mass}}{\text{Molar mass}}$

For $3.5$ g ${\text{N}}_2$: $n=\frac{3.5}{28}=0.125$ mol

For $0.5$ g ${\text{H}}_2$: $n=\frac{0.5}{2}=0.25$ mol

For $3.2$ g ${\text{O}}_2$: $n=\frac{3.2}{32}=0.1$ mol

For $4.6$ g ${\text{NO}}_2$: $n=\frac{4.6}{46}=0.1$ mol

Since $0.5$ g ${\text{H}}_2$ has the maximum number of moles, it contains the maximum number of molecules.

Answer: $0.5$ g ${\text{H}}_2$