Chemical Thermodynamics Question 232

Question: If enthalpies of formation of C2H4(g),,CO2(g) and H2O(l) at 25oC and 1,atm pressure be 52, - 394 and 286,kJ,mol1 respectively, the enthalpy of combustion of C2H4(g) will be [CBSE PMT 1995; AIIMS 1998; Pb. PMT 1999]

Options:

A) +1412,kJ,mol1

B) 1412,kJ,mol1

C) +141.2,kJ,mol1

D) 141.2,kJ,mol1

Show Answer

Answer:

Correct Answer: B

Solution:

C2H4+3O22CO2+2H2O

ΔHreaction=[2×ΔHfo(CO2)+2×ΔHfo,(H2O)]

[ΔHfo,(C2H4)+,3×ΔHfo,(O2)]

=[,2,(,394)+2,(,286)][52+0]=1412,kJ .



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