For the change C (diamond) `rarr` C(graphite) , `Delta H=-1.89` KJ, if 6 g of diamond and 6g of graphite are seperately burnt to yield `CO_(2)` the heat liberated in first case is :

Options

A. less than in the second case by 1.89 kJ
B. less than in the second case by 11.34 kJ
C. less than in the second case by 14.34 kJ
D. more than in the second case by 0.945 kJ

Answer

A

Explanation

`C_(D)toC_(G):DeltaH=-1.89`
`C_(D)+O_(2) to CO_(2),DeltaH=-q_(1)`
`underline{:(C_(G),+,O_(2),to,CO_(2),,,DeltaH=-q_(2)),(-,,-,,-,," "+):}`
`C_(D)toC_(G),DeltaH=-q_(1)+q_(2)`
`-q_(1)+q_(2)=1.89`
or `q_(2)-q_(1)=-1.89` for 12 g
`C_(D)toC_(C)`
thus, for 6g `C_(D)toC_(C)`
`q_(2)-q_(1)=(-1.89)/(2)=-0.945`