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

D

Explanation

`C_D rarr C_G , Delta H=-1.89` kJ
`C_D+O_2 rarr CO_2, Delta H =- q_1 `
`C_G+O_2 rarr CO_2 , Delta H = -q_2`
`overset(- " "-" "-" "+)bar(C_DrarrC_G,DeltaH=- q_1+q_2)`
`-q_1 +q_2 = 1.89 kJ `
or `q_2-q_1 =- 1.89 kJ for 12 g C_D rarr C_C `
Thus for 6 g `C_D rarr C_C `
`q_1 -q_1 =(-1.89 kJ )/(2) =- 0945 kJ `