Acetylene (C2H2, molar mass 26g/mol) can be produced by the reaction of calcium carbide with water according to the following equation:

Question

CaC2(s) + 2H2O(l) = C2H2(g) + Ca(OH)2 (aq).

If 2.0g of calcium carbide is reacted at STP, what is the volume of acetylene produced?

 

a) 0.076 L

b) 1.7 L

c) 3.4 L

d) 0.85 L

e) 2.0L

Answer 1

CaC₂(s) + 2H₂O(l) = C₂H₂(g) + Ca(OH)2 (aq)

moles CaC₂ = 2.0 g x 1 mole/64.1g = 0.0312 moles

moles C₂H₂ formed = 0.0312 moles CaC₂ x 1 mole C₂H₂/mole CaC₂ = 0.0312 moles C₂H₂ (assuming H₂O is not limiting)

At STP 1 mole of an ideal gas = 22.4 liters.

Volume C₂H₂ produced = 0.0312 moles x 22.4 L/mole = 0.699 liters