Question

1.0 g of H2 has the same number of molecules as in:

• A. 14 g of N2
• B. 18 g of H2O
• C. 16 g of CO
• D. 28 g of N2

Answer 1

Answer: (A)

14 g of N2

Answer 2

The number of moles (n) is given by: $n = \frac{mass (g)}{molar mass (g/mol)}$. The number of molecules is given by $N = nN_A$, where $N_A$ is Avogadro's number.
For 1.0 g of H$_2$: Molar mass of H$_2$ = 2.016 g/mol Moles of H$_2 = \frac{1.0 g}{2.016 g/mol} \approx 0.496$ mol
Number of molecules = 0.496 $\times$ $N_A$
Let's check the options:
(1) 14 g of N$_2$: Molar mass of N$_2$ = 28 g/mol Moles of N$_2 = \frac{14 g}{28 g/mol} = 0.5$ mol Number of molecules = 0.5 $\times$ $N_A$
Thus, 14 g of N$_2$ has approximately the same number of molecules as 1 g of H$_2$.