Calculate the standard heat of formation of carbon disulphide (l). Given that the standard heats of combustion of carbon (s), sulphur (s) and carbon disulphide (l) are -393.3, -293.72 and -1108.76 kJ `mol^(-1)` respectively.

Explanation

Objective reaction : `C(s)+25(s)rarr CS_(2)(l) , Delta H = ?`
Given that (1) `C(s)+O_(2)O_(2)(g)rarr CO_(2)(g) , Delta H_(1)=-393.3 kJ mol^(-1)`
(2) `S(s)+O_(2)(g)rarr SO_(2)(g)rarr SO_(2)(g) , Delta H_(2)=-293.72 kJ mol^(-1)`
(3) `CS_(2)(l)+3O_(2)(g)rarr CO_(2)(g)+2SO_(2)(g) , Delta H_(3)=-1108.76 kJ mol^(-1)`
To obtained objective reaction.
equation (1) + 2x equation (2) - equation (3)
`therefore Delta H = Delta H_(1)+2Delta H_(2)-Delta H_(3)`
`=-393.3+2(-293.72)-(-1108.76)`
`=128.02 kJ`