One Mole of Methane — Everything You Need to Know

Methane formula: CH₄ Molar mass calculation: • C: 12 g/mol • H: 1 g/mol × 4 = 4 g/mol • Molar mass of CH₄ = 12 + 4 = 16 g/mol

For ONE mole (1 mol) of CH₄:

1. Mass = 16 g

2. Number of molecules: = 1 × Avogadro's number (Nₐ) = 6.022 × 10²³ molecules

3. Number of C atoms: = 1 × 6.022 × 10²³ = 6.022 × 10²³ atoms (1 C per CH₄ molecule)

4. Number of H atoms: = 4 × 6.022 × 10²³ = 24.088 × 10²³ atoms (4 H per CH₄ molecule)

5. Volume at STP (0°C, 1 atm): = 22.4 L (molar volume of any ideal gas at STP)

The mole is the SI unit for amount of substance: • 1 mol = 6.022 × 10²³ particles (Avogadro's number)

For CH₄: Atoms per molecule: C=1, H=4, Total=5 atoms per molecule

Atom counting per mole of CH₄: • Total atoms = 5 × Nₐ = 5 × 6.022 × 10²³ = 30.11 × 10²³ atoms • C atoms = 1 × Nₐ = 6.022 × 10²³ • H atoms = 4 × Nₐ = 24.088 × 10²³

Moles of atoms in 1 mol CH₄: • 1 mol of C atoms • 4 mol of H atoms • 5 mol of atoms total

Useful calculations: • 2 mol CH₄ = 32 g, contains 2 × Nₐ molecules • 8 g CH₄ = 8/16 = 0.5 mol = 0.5 × Nₐ molecules • 32 g CH₄ = 2 mol = 44.8 L at STP

Combustion equation: CH₄ + 2O₂ → CO₂ + 2H₂O

For 1 mol of CH₄: • Reacts with 2 mol O₂ (= 64 g O₂ = 44.8 L at STP) • Produces 1 mol CO₂ (= 44 g = 22.4 L at STP) • Produces 2 mol H₂O (= 36 g) • Energy released: ~890 kJ/mol (standard enthalpy of combustion)

CH₄ in natural gas: • Natural gas is primarily methane (~95%) • Molar mass: 16 g/mol (lightest hydrocarbon) • Density at STP: 16/22.4 = 0.714 g/L • Less dense than air (average molar mass ~29 g/mol) → natural gas rises if leaked

Physical properties of methane: • Gas at room temperature (bp = −161.5°C) • Colourless, odourless • Greenhouse gas (21× more potent than CO₂ over 100 years)