Using Delta_fH deg(C2H4(g))=+52.3, Delta_fH deg(CO2(g))=-393.5 and Delta_fH deg(H2O(l))=-285.8 kJ mol^-1, find Delta H deg for C2H4(g) + 3O2(g) -> 2CO2(g) + 2H2O(l).

JEE Main levelSingle correct optionDifficulty 2 of 3td129

Using $Δ_{f} H^{\circ} (C X_{2} H X_{4} (g)) = + 52.3$ , $Δ_{f} H^{\circ} (CO X_{2} (g)) = - 393.5$ and $Δ_{f} H^{\circ} (H X_{2} O (l)) = - 285.8 kJ mo l^{- 1}$ , find $Δ H^{\circ}$ for $C X_{2} H X_{4} (g) + 3 O X_{2} (g) 2 CO X_{2} (g) + 2 H X_{2} O (l)$ .

Δ H^{\circ} = \sum ν Δ_{f} H^{\circ} (products) - \sum ν Δ_{f} H^{\circ} (reactants) = 2 (- 393.5) + 2 (- 285.8) - (+ 52.3) = - 1410.9 kJ

. Ignoring the coefficients gives

- 731.6

, adding the

C X_{2} H X_{4}

term gives

- 1306.3

, and using

H X_{2} O (g)

gives

- 1322.9