Compare quantity of heat produced by the combustion of 1.0 g glucose `(C_6H_12O_6)` with that produced by 1.0g sucrose `(C_12H_22O_11)`. Given that the standard heats of formation of `CO_(2), H_(2)O` glucose and sucrose are `-393.5, -285.9, -1260 and -2221 kJ mol^(-1)` respectively.

Answer

`Delta H `for glucose `= - 15.6 kJ g^(-1),DeltaH` for the sucrose `= - 16.5 kJ g^(-1)`

Explanation

`C_(6)H_(12)O_(6)+ 6O_(2)rarr 6CO_(2)+6H_(2)O`
`Delta_(r) H^(@) = [ 6 Delta_(r)H^(@) (CO_(2))+6Delta_(r) H^(@)( H_(2)O) ] = [ Delta_(r)H^(@) ( C_(6) H_(12)O_(6))+ 6 Delta_(f) H^(@) (O_(2))]`
`= [6( - 393.5) + 6( -285.9)]-[(- 1260)+ 6(0)] = - 2816kJ mol^(-1)`
`:. `Heat produced from 1g glucose `= ( 2816.4)/( 180) =15.6 kJ `
`C_(12) H_(22)O_(11)+ 12O_(2) rarr 12CO_(2) + 11H_(2)O`
`Delta_(r)H^(@) =[ 12 ( - 393.5) +11( - 285.9) ] - [ -2221+0]= -5645.9 kJ mol^(-1)`
`:.` Heat produced from 1 g sucrose ` =( 5645.9 ) /(342) kJ = 16.5 kJ `