Question

The standard enthalpies of formation of`CO_(2)(g), H_(2)O(l) ` and glucose (s)at `25^(@)C` are`-400 kJ //mol, - 300 kJ//mol` and`-1300kJ//mol` respectively.The standard enthalpy of combustion per gram of glucose at`25^(@)C` is
A. ` + 2900kJ`
B. ` -2900kJ`
C. ` - 16.11kJ `
D. `+16.11 kJ`

Answer 1

Correct Answer - C
`C_(6)H_(12)O_(6)(s)+ 6O_(2)(g)rarr6 CO_(2)(g) +6 H_(2)O(l) `
`Delta_(r)H^(@) =Delta_(c) H^(@) = [ 6 Delta_(f)(CO_(2)) + 6 Delta_(f)H^(@) ( H_(2)O)]- [ Delta_(f) H^(@) ( C_(6)H_(12)O_(6)) + 6 Delta_(f) H^(@) ( O_(2))]`
`= 6 xx ( - 400) + 6 ( - 300) -( - 1300)`
`= -2900 kJ`
`= - ( 2900)/( 180 ) kJ //g =- 16.11 kJ //g`