In the reaction `CS_(2)(l)+3O_(2)(g)rarrCO_(2)(g)+2SO_(2)(g)DeltaH= -265 kcal`
The enthalpies of formation of `CO_(2)` and `SO_(2)` are both negative and are in the ratio `4:3`. The enthalpy of formation of `CS_(2)` is `+26 kcal//mol`. Calculate the enthalpy of formation of `SO_(2)`.

Options

A. -90 kcal/ mol
B. -52 kcal / mol
C. -78 kcal/ mol
D. -71.7 kcal/ mol

Answer

D

Explanation

`CS_(2(l))+3O_(2(g)) rarr CO_(2(g)) + 2SO_(2)+2SO_(2),`
`Delta H =-265 kal`
Let `Delta H_(f) [CO_(2(g))]=4x and Delta H_(f) [SO_(2(g))]=3x`
`Delta H_("reaction") = Delta H_(f) [CO_(2(g))]=2 Delta H_(f) [SO_(2(g))]-Delta H_(f) [CS_(2(l))]`
`-265 =4x+6x-26" "therefore x=-23.9`
`therefore Delta H_(f) [SO_(2(g))]=3x=-71.7" kcal / mol"`