Chemical Thermodynamics Question 421

Question: Standard enthalpy of combustion of CH3 is ,890kJmol1 and standard enthalpy of vaporisation of water is 40.5kJmol1 . The enthalpy change of the reaction CH4(g)+2O2(g)CO2(g)+H2O(g)

Options:

A) 809.5kJmol1

B) 890kJmol1

C) 809kJ,mol1

D) 971kJ,mol1

Show Answer

Answer:

Correct Answer: A

Solution:

  • CH4(g)+2O2(g)CO2(g)+2H2O(l)

ΔH=890kJ …. (i) 2H2O(l)2H2O(g);

ΔH=2×40.5=81kJ …. (ii) From (i) + (ii), we get CH4(g)+2O2(g)CO2(g)+2H2O(g)

ΔH=890+81=809kJ



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