Which of the following contains the highest number of helium atoms?

Question

Accepted Answer

1. **Analyze Option A (4 u):** The unified atomic mass unit ('u') represents the mass of a single atom on the atomic scale. Since the atomic mass of Helium is 4 u, this option corresponds to exactly **1 atom**.
2. **Analyze Option B (4 g):** The molar mass of Helium is $4 	ext{ g mol}^{-1}$.
   $$ 	ext{Moles} = \frac{4 	ext{ g}}{4 	ext{ g mol}^{-1}} = 1 	ext{ mol} $$
   Total atoms = $1 	imes N_A = 6.022 	imes 10^{23}$ atoms [Class 11 Physics, Appendix A 3].
3. **Analyze Option C (2.27 L at STP):** Using the standard molar volume at STP ($22.7 	ext{ L mol}^{-1}$ for 1 bar pressure):
   $$ 	ext{Moles} = \frac{2.27 	ext{ L}}{22.7 	ext{ L mol}^{-1}} = 0.1 	ext{ mol} $$
   Total atoms = $0.1 	imes N_A$ atoms.
4. **Analyze Option D (4 mol):**
   Total atoms = $4 	imes N_A$ atoms.
5. **Conclusion:** Comparing the magnitudes: $4 N_A$ (Option D) > $1 N_A$ (Option B) > $0.1 N_A$ (Option C) > 1 atom (Option A).

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