Question

A standard heat of formation of CS2 (I) will be:, given that the standard heat combustion of carbon(s), Sulphur(s) and $C{S}_2\left(l\right)$ are $-393.3,-293.72and-1108.76Kj/mol$ respectively.

Answer 1

$C{S}_2+3O_2\to C{O}_2+2S{O}_2\Delta H=-1108.76KJmo{l}^{-}1$

$C+O_2\to C{O}_2\Delta H=-393.3KJmo{l}^{-}1$

$S+O_2\to S{O}_2\Delta H=-293.72KJmo{l}^{-}1$

$\Delta H=H_p-H_R$

$=[\Delta H_C^0{O}_2+\Delta H_S^0{O}_2]$$-[\Delta H_C^0{S}_2+3\Delta H^0{O}_2$

$-1108.76=[-393.3+(-293.72)-\Delta H_C^0{S}_2](sinceenthalpyofformationofoxygen=0)$

$\Delta H_C^0{S}_2=[-393.3+(-293.72\left)\right]+11.08$

$=421.74KJ/mol$