The heat of combustion of ethyl alcohol is 34,600 cals. The heat of formation of `CO_(2)` and water are `-96.200 and -68.000` calories respectively at constant pressure. What is the heat formation of ethyl alcohol ?
Given :
`DeltaH_(f)^(@),CO_(2)=-96200 " cal" , DeltaH_(f)^(@),H_(2)O=-68000 cal `
`DeltaH_(c)^(@),C_(2)H_(5)OH=34.600 cal `

Explanation

`C_(2)H_(5)OH_((l))+3O_(2_((g)))rarr2CO_(2_((g)))+3H_(2)O_((l))`
`DeltaH^(@)=sumH_("product")^(@)-sumH_("Reactants")^(@)`
`=(-2xx96200)+(-3xx68000)-34600`
`=-192400-204000-34600=-431000`
`DeltaH^(@)=--431000cal.`