H2(g)+12O2(g)→H2O(l);ΔH at 298K=−285.8kJ The molar enthalpy of vaporization of water at 1 atm and 25oC is 44kJ. The standard enthalpy of formation of 1 mole of water vapour at is ?
A
−241.8kJ
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B
241.8kJ
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C
329.8kJ
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D
−329.8kJ
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Solution
The correct option is C−241.8kJ H2(g)+12O2(g)→H2O(l);ΔH at 298K=−285.8kJ......(1)
The
molar enthalpy of vaporization of water at 1 atm and 25oC is 44kJ.
H2O(l)→H2O(g);ΔH=44kJ......(2)
Add equations (1) and (2)
H2(g)+12O2(g)→H2O(g);ΔH at 298K=−285.8+44=−241.8kJ
The standard enthalpy of formation of 1 mole of water vapour at
is −241.8kJ