The heat of combustion of gaseous methane (CH4) at constant volume is measured in a bomb calorimeter at 298 K and is found to be −885.4kJmol−1 . Find the value of enthalpy change.
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Solution
Combustion of CH4-
CH4(g)+2O2(g)⟶CO2(g)+2H2O(l)
Δng=nP−nR=1−(2+1)=−2
Given:- ΔU=−885.4kJ/mol
T=298K
As we know that,
ΔH=ΔU+ΔngRT
⇒ΔH=−885.4+(−2×8.314×10−3×298)
⇒ΔH=−885.4−4.95=−890.05kJ/mol
Hence the value of enthalpy change is −890.05kJ/mol.