The enthalpy change for the combustion of ethanol at 298 K and 1 atm is given below
CH3-CH2OH(l) + 3O2(g)------------à 2CO2 (g)+ 3H2O(l) ∆H=-1363Kj.Calculate the internal energy change for the above reaction?
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Solution
From first law of Thermodynamics, DelH=DelU+Deln RT Del H =Heat of reaction DelU=Internal energy change where Deln is the change in the no.of moles of gaseous substance=2-3=-1(since 2 moles from CO2 and 3 from O2) => DelH=-1,363kJ DelU=DelH-Del n*RT =>DelU=-1363-(-1)*8.314*298 =>DelU=-1338.22428 =>DelU=-1338.22kJ