B) 2c2h2(g) + 5o2(g)⟶4co2(g) + 2h2o(l) 6.54 calculate the heats of combustion for the following reactions from the standard enthalpies of formation listed in appendix 2: (a) c2h4(g) + 3o2(g) ⟶2co2(g) + 2h2o(l) (b) 2h2s(g) + 3o2(g) ⟶2h2o(l) + 2so2(g)

a.  ΔH⁸ =  -1420 kJ/mol       b. ΔH⁸ =  -1144.84 kJ/mol

Explanation:

a.

                 C₂H₄ (g) + 3 O₂ (g)  4 CO₂ (g) + 2 H₂O (l)  ΔH⁸ = ?

ΔH⁸f  kJmol  52.47       0                                      -399.5            -285.83

ΔH⁸ = 2(-399.5) + 2 (-285.83) - (52.47)

ΔH⁸ =  -1420 kJ/mol

b.

                       H₂S (g) + 3 O₂ (g) 2 H₂O (l)  + 2 SO₂ (g)

ΔH⁸f  kJmol     -20.50     0                                    -285.83      -296.84

ΔH⁸ =  2(-285.83) + 2 (-296.84) - (-20.50)

ΔH⁸ =  -1144.84 kJ/mol

the answer is 0.8m.

by: nicholas