Question

Determine the heat of reaction (ΔHrxn) for the combustion of ethanol (C2H5OH) by using heat of formation data: C2H5OH (l) + 3 O2 (g) → 2 CO2 + 3 H2O (g)

Answer 1

`\Delta H_(rxn)=-1234.782kJ`

Step-by-step explanation:

`\Delta H_(rxn)=\sum [n_(i)* \Delta H_(f)^(0)(product)_(i)]-\sum [n_(j)* \Delta H_(f)^(0)(reactant_(j))]`

Where
`n_(i)` and
`n_(j)` are number of moles of product and reactant respectively (equal to their stoichiometric coefficient).

`\Delta H_(f)^(0)` is standard heat of formation.

So,
`\Delta H_(rxn)=[2mol* \Delta H_(f)^(0)(CO_(2))_(g)]+[3mol* \Delta H_(f)^(0)(H_(2)O)_(g)]-[1mol* \Delta H_(f)^(0)(C_(2)H_(5)OH)_(l)]-[3mol* \Delta H_(f)^(0)(O_(2))_(g)]`

or,
`\Delta H_(rxn)=[2mol* -393.509kJ/mol]+[3mol* -241.818kJ/mol]-[1mol* -277.69kJ/mol]-[3mol* 0kJ/mol]`

or,
`\Delta H_(rxn)=-1234.782kJ`