Question

Calculate (using bond energies) the heat of reaction (per mole of CO, in KJ/Mol) for the combustion of CO into CO₂. Balance and do not round final answer

Calculate (using bond energies) the heat of reaction (per mole of C₂H₂ in KJ/Mol) for the combustion of C₂H₂ into CO₂ and water. Balance and do not round final answer

Answer 1

2CO + O₂ --------> 2CO₂

Bond Energy (CO) = 1074 kJ, Bond Energy (O=O) = 499 kJ, Bond Energy(C=O) = 802 kJ.

bonds broken

2 CO = 2 x 1074 = 2148 KJ

O=O = 1x 490.4 = 490.4 KJ          

Bond Forming

4 x C=O = 4 x 802 = 3208 Kj

ΔH^o_(reaction) = ΣH_{(reactant bonds broken)} - ΣH_{(product bonds formed)}

                  = 2638.4- 3208 = -569.6KJ

ΔH^o_{(reaction) =} -569.6KJ

Remember that the minus sign means "energy released"

2C₂H_{2 +} 5O₂ ---------> 4CO₂ + 2H₂O

Bond energy C≡C 835 KJ   Bond energy H-C 411 KJ Bond Energy (O=O) = 499 kJ Bond Energy(C=O) = 802 kJ   Bond energy H-O 459 KJ

Bonds broken

2 C≡C = 2 x 835 = 1670 KJ

2 C-H = 2 x 411 = 822 KJ

5 x O=O = 5 x 499 = 2495 KJ

Bond Forming

4 x C=O = 8 x 802 = 6416 KJ

4 x O-H = 4 x 459 = 1836 KJ

ΔH^o_(reaction) = ΣH_{(reactant bonds broken)} - ΣH_{(product bonds formed)}

                        = 4987- 8252

    ΔH^o_(reaction) = -3265 KJ