How many atoms are contained in 0.2moles of nitrogen? $[N_{A} = 6.02 \times 10^{23}]$

Analyze the question: We need the number of atoms in 0.2 mol of nitrogen. The key is whether "nitrogen" means N atoms or N₂ molecules.

Concept: Number of particles = moles × Avogadro's number

• If 0.2 mol of nitrogen atoms (N): 0.2 × 6.02 × 10²³ = 1.204 × 10²³ atoms, which is option A.
• If 0.2 mol of nitrogen gas (N₂, diatomic): molecules = 0.2 × 6.02 × 10²³ = 1.204 × 10²³ molecules. Each molecule has 2 atoms, so atoms = 2 × 1.204 × 10²³ = 2.408 × 10²³ ≈ 2.41 × 10²³, which is option B.

Which to choose? Nitrogen exists naturally as the diatomic molecule N₂. The question asks for "atoms" in "nitrogen", which suggests the molecule-to-atom conversion is being tested.

Step-by-step solution:

1. Molecules of N₂ = 0.2 × 6.02 × 10²³ = 1.204 × 10²³
2. Atoms per molecule = 2
3. Total atoms = 1.204 × 10²³ × 2 = 2.408 × 10²³ ≈ 2.41 × 10²³

Answer: B

Tip: When a question asks for atoms in a diatomic gas (H₂, N₂, O₂, Cl₂, F₂), multiply the molecule count by 2. If it says "nitrogen atoms", don't multiply. Always check the wording carefully.