Balance the chemical equation: C2H5OH + O2 -> CO2 + H2O. Use the balanced equation to show conservation of atoms.

Balance the chemical equation: $\ce C 2 H 5 O H + O 2 - > C O 2 + H 2 O$ . Use the balanced equation to show conservation of atoms.

hard 4 marks Class 9 · Science · Atoms and Molecules

Answer

\ce C 2 H 5 O H + 3 O 2 - > 2 C O 2 + 3 H 2 O

The correct answer is $\ce C 2 H 5 O H + 3 O 2 - > 2 C O 2 + 3 H 2 O$ — Check conservation: - C: 2 = 2. - H: 6 = 6. - O: 1+6 = 7 on both sides.

Identify atoms to be balanced: C, H, O.
Assign coefficients: let ethanol be 1, O₂ be x, CO₂ be y, H₂O be z. - Carbon balance: 2 (from ethanol) = y → y = 2. - Hydrogen balance: 6 (from ethanol) = 2z → z = 3. - Oxygen balance: Ethanol contributes 1 O, O₂ contributes 2x O. On the product side, CO₂ contributes 2·2 = 4 O, H₂O contributes 3·1 = 3 O. So total O on right = 7. - Set left O = right O: (1 + 2x = 7) → (2x = 6) → (x = 3).
Write the balanced equation: $\ce C 2 H 5 O H + 3 O 2 - > 2 C O 2 + 3 H 2 O$ .
Check conservation: - C: 2 = 2. - H: 6 = 6. - O: 1+6 = 7 on both sides.

Common mistake: Using incorrect coefficient for O₂ or forgetting to balance all atoms

Concept tested: Balancing chemical equations