Solved: CHEMISTRY Question for NEET

NEET CHEMISTRYEasy

Which of the following has the greatest number of molecules?

64 g SO₂

44 g CO₂

48 g O₃

8 g H₂

Identify the Formula: The number of molecules ( $N$ ) in a given mass ( $m$ ) of a substance is calculated using the number of moles ( $n$ ) and Avogadro's constant ( $N_A \approx 6.022 \times 10^{23} \text{ mol}^{-1}$ ). $n = \frac{\text{Mass (g)}}{\text{Molar Mass (g/mol)}}$ $N = n \times N_A$ [Class 12 Chemistry, Ch 1, Example 1.1; Class 11 Physics, Appendix A 3]
Calculate Moles for each option:

Option A ( $64\text{ g SO}_2$ ): Molar Mass of $\text{SO}_2 = 32 + 2(16) = 64\text{ g/mol}$ . $n = \frac{64}{64} = 1\text{ mol} \implies 1 N_A \text{ molecules}$
Option B ( $44\text{ g CO}_2$ ): Molar Mass of $\text{CO}_2 = 12 + 2(16) = 44\text{ g/mol}$ . $n = \frac{44}{44} = 1\text{ mol} \implies 1 N_A \text{ molecules}$
Option C ( $48\text{ g O}_3$ ): Molar Mass of $\text{O}_3 = 3(16) = 48\text{ g/mol}$ . $n = \frac{48}{48} = 1\text{ mol} \implies 1 N_A \text{ molecules}$
Option D ( $8\text{ g H}_2$ ): Molar Mass of $\text{H}_2 = 2(1) = 2\text{ g/mol}$ . $n = \frac{8}{2} = 4\text{ mol} \implies 4 N_A \text{ molecules}$

Conclusion: $8\text{ g of H}_2$ contains the greatest number of molecules ( $4 N_A$ ).

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