3.9.5: Lecture Demonstration- Carbide Cannon

Enthalpy of reactions:

Assuming you want about a 1 kJ explosion, how much CaC₂ would you add to a carbide cannon?

(1) 2 C₂H₂ + 5 O₂ → 4 CO₂ + 5 H₂O ΔH ?

given

(2) C + O₂ → CO₂ ΔH_f = -393.5 kJ/mol

(3) H₂ + 1/2 O₂ → H₂O (g) Δ H_f = -241.82 kJ/mol

(4) 2 C + H₂ → C₂H₂(g) ΔH_f = +226.7

Calculated enthalpy change for combustion of 2 mol of acetylene, ΔH = -2511 kJ

This is 48.2 kJ/g

for 1 kJ, we need 1 kJ/48.2 kJ/g = 0.02 g of acetylene

CaC₂ + 2 H₂O → HCCH + Ca(OH)₂

this requires 0.0008 mol of CaC₂, which is 0.05 g.

Do it with a Bangsite Cannon!

Contributors

• Ed Vitz (Kutztown University), John W. Moore (UW-Madison), Justin Shorb (Hope College), Xavier Prat-Resina (University of Minnesota Rochester), Tim Wendorff, and Adam Hahn.