Question

Identify the pair that contains the same number of atoms.

• A. 8 g of Helium and 4 g of Hydrogen
• B. 2 g of Hydrogen and 16 g of Oxygen
• C. 14 g of Nitrogen and 16 g of Oxygen
• D. 16 g of Oxygen and 8 g of Helium

Answer 1

The correct option is C 14 g of Nitrogen and 16 g of Oxygen

The gram atomic masses of the given atoms are as follows:
$H=1,\mathrm{He}=4,N=14,O=16$
The same number of moles of a pair of atoms corresponds to the same number of atoms.
Now,
$\mathrm{Number}\mathrm{of}\mathrm{moles}=\frac{\mathrm{Given}\mathrm{mass}}{\mathrm{Gram}\mathrm{atomic}\mathrm{mass}}$
I. 2 g of Hydrogen and 16 g of Oxygen

Number of moles of H = $\frac{2}{1}=2$
Number of moles of O = $\frac{16}{16}=1$

II. 14g of Nitrogen and 16 g of Oxygen

Number of moles of N = $\frac{14}{14}=1$
Number of moles of O = $\frac{16}{16}=1$

III. 8 g of Helium and 4 g of Hydrogen

Number of moles of He = $\frac{8}{4}=2$
Number of moles of H = $\frac{4}{1}=4$

IV. 16 g of Oxygen and 8 g of Helium

Number of moles of O = $\frac{16}{16}=1$
Number of moles of He = $\frac{8}{4}=2$

Thus, among the given pairs, 14 g of nitrogen and 16 g of oxygen contain the same number of atoms.