Question

Which of the following contains the largest number of molecules?

• A. 0.2 mole of H${}_2$
• B. 8.0 mole of H${}_2$
• C. 17 g of H${}_2$O
• D. 6.0 g of CO${}_2$

Answer 1

The correct option is B 8.0 mole of H${}_2$

1 mole of any substance contains $6.02\times {10}^{23}$ (Avogadro's number ) of molecules.

A. 0.2 mole of H${}_2$ contains $0.2\times 6.02\times {10}^{23}=1.2\times {10}^{23}$ molecules.

B. 8.0 mole of H${}_2$ contains $8.0\times 6.02\times {10}^{23}=4.8\times {10}^{24}$ molecules.

C. 17 g of H${}_2$O $=\frac{\text{17 g}}{\text{18 g/mol}}=\text{0.94 moles}$

17 g of H${}_2$O contains $0.94\times 6.02\times {10}^{23}=5.7\times {10}^{23}$ molecules.

D. 6.0 g of CO${}_2$ $=\frac{\text{6.0 g}}{\text{44 g/mol}}=\text{0.136 moles}$

6.0 g of CO${}_2$ contains $0.136\times 6.02\times {10}^{23}=8.2\times {10}^{22}$ molecules.

Hence, 8.0 mole of H${}_2$ contains the largest number of molecules