A sample contains 3 moles of nitrogen gas (N₂). What is the mass of the sample?

Explanation

Step 1: Understand the molecular formula
Nitrogen gas exists as N₂ (diatomic molecules)
Each molecule contains 2 nitrogen atoms bonded together

Step 2: Calculate molar mass of N₂
Atomic mass of nitrogen (N) = 14 g/mol
Molar mass of N₂ = 2 × 14 = 28 g/mol

Step 3: Use the formula: mass = moles × molar mass
Given: 3 moles of N₂
Mass = 3 moles × 28 g/mol
Mass = 84 grams

Important: Don’t confuse atomic mass (14 g/mol for one N atom) with molecular mass (28 g/mol for N₂). Nitrogen gas always exists as N₂ molecules in nature.