Given C_(s) + O_2(g) → CO_2(g); ΔH = – 395 KJ
S_(s) + O_2(g) → SO_2(g); ΔH = – 295 KJ
CS_2(l) +3O_2(g) → CO_2(g) + 2SO_2(g); ΔH = – 1110 KJ
The heat of foramation of CS_2(l) is

.eq.(1) +2 eq.(2) - eq (3)

(eq. = equation)

        C_(s) + O_2(g) → CO_2(g); ΔH₁ = – 395 KJ

     2S_(s) +2 O_2(g) →2 SO_2(g); ΔH₂ =2( – 295) KJ

CO_2(g) + 2SO_2(g) →CS_2(l) +3O_2(g) ; ΔH₃ = + 1110 KJ

    C_(s) + 2S_(s) → CS_2(l) ;  ΔH_f = ΔH₁ + ΔH₂ + ΔH₃

                                         ΔH_f(CS₂)  = +125 KJ/mole