Given that:
i. `C("graphite") +O_(2)(g) rarr CO_(2)(g), DeltaH =- 393.7 kJ`
ii. `C("diamond") rarr C("graphite"), DeltaH =- 2.1 kJ`
a. Calculate `DeltaH` for buring of diamond of `CO_(2)`.
b. Calculate the quantity of graphite that must be burnt to evolve `5000 kJ` of heta.

Explanation

a. To calculate `DeltaH` of the reaction
`C("diamond") +O_(2)(g) rarr CO_(2)(g), DeltaH = ?`
`DeltaH = DeltaH_(1) +DeltaH_(2)`
`=- 393.7 - 2.1 =- 395.8 kJ`
b. `1`mole of `C`(graphite)
i.e. `12 g` on buring evolves heat `= 393.7 kJ`
`393.7 kJ` of heat obtained from `- 12 gC`
`:. 5000 kJ` of heta is evolved from `= (12 xx 5000)/(393.7)`
`= 152.4 g` of graphite