Question

3. Acetylene gas, C2H2, is used in welding, produces an extremely hot flame when it burns in pure oxygen according to the following reaction.

2 C2H2 + 5O2 🡪 4CO2 + 2H2O

How many moles of water (H2O) are produced when 25.0 grams of C2H2 burns completely?

Answer 1

Balanced equation: 2 C2H2 + 5 O2 → 4 CO2 + 2 H2O, so 2 mol C2H2 produce 2 mol H2O (1:1 mole ratio).

Molar mass C2H2 = 2(12.01) + 2(1.008) = 26.04 g·mol⁻¹

Moles C2H2 = 25.0 g / 26.04 g·mol⁻¹ = 0.960 mol

Therefore moles H2O produced = 0.960 mol.