Calcium carbide reacts with water vapour to produce acetylene according to the equation: CaC₂ + 2 H₂O → C₂H₂ + Ca(OH)₂. If 56.0 g of CaC₂ is reacted completely with excess water vapour, calculate the volume of acetylene gas produced at NTP (1 mol gas = 22.4 L).
Answer
19.6 L of acetylene at NTP
The correct answer is 19.6 L of acetylene at NTP — Round to three significant figures: 19.6 L.
Step-by-step solution
- Calculate the molar mass of CaC₂: Ca = 40.08 g mol⁻¹, C = 12.01 g mol⁻¹ (×2) → 40.08 + 24.02 = 64.10 g mol⁻¹.
- Find moles of CaC₂ used: 56.0 g ÷ 64.10 g mol⁻¹ = 0.873 mol.
- From the balanced equation, 1 mol CaC₂ yields 1 mol C₂H₂, so moles of acetylene formed = 0.873 mol.
- Use the molar volume at NTP: V = n × 22.4 L mol⁻¹ = 0.873 × 22.4 L = 19.55 L.
- Round to three significant figures: 19.6 L.
Common mistake: Using the molar volume 24 L mol⁻¹ (STP) instead of 22.4 L mol⁻¹ for NTP, which gives an incorrect volume.
Concept tested: Production of acetylene from calcium carbide
Published · How this solution was prepared and checked
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