Answer to Question #270593 in Organic Chemistry for Lia

Question

Acetylene, C₂H₂, is a gas commonly used in welding. It is formed in the reaction of calcium carbide, CaC₂, with water. Given the thermochemical equations below, calculate the value of ΔH°_f for acetylene in units of kilojoules per mole:

(a) CaO(s) + H₂O(ℓ) ---> Ca(OH)₂(s) ΔH° = −65.3 kJ

(b) 2CaO(s) + 5C(s, gr) ---> 2CaC₂(s) + CO₂(g) ΔH° = +753 kJ

(c) CaCO₃(s) ---> CaO(s) + CO₂(g) ΔH° = +178 kJ

(d) CaC₂(s) + 2H₂O(ℓ) ---> Ca(OH)₂(s) + C₂H₂(g) ΔH° = −126 kJ

(e) C(s, gr) + O₂(g) ---> CO₂(g) ΔH° = −393.5 kJ

(f) 2H₂O(ℓ) ---> 2H₂(g) + O₂(g) ΔH° = +572 kJ

Here is the target equation:

2C(s, gr) + H₂(g) ---> C₂H₂(g)

Answer 1

-65.3+753+178-(126+572)

=167.7kJ