If, i) C + 2S arrow CS_2 , Δ H = 117\ kJ ii) C + O_2 arrow CO_2 , Δ...

The required reaction for the combustion of $\text{CS}_2$ is:

$\text{CS}_2 + 3\text{O}_2 \rightarrow \text{CO}_2 + 2\text{SO}_2$

This reaction can be obtained by applying Hess's Law using the given equations.

Reversing equation (i):
$\text{CS}_2 \rightarrow \text{C} + 2\text{S}$, $\Delta H_1' = -117\ \text{kJ}$

Keeping equation (ii) as it is:
$\text{C} + \text{O}_2 \rightarrow \text{CO}_2$, $\Delta H_2' = -393\ \text{kJ}$

Multiplying equation (iii) by $2$:
$2\text{S} + 2\text{O}_2 \rightarrow 2\text{SO}_2$, $\Delta H_3' = 2 \times (-297) = -594\ \text{kJ}$

Adding the above three equations, we get the required reaction:
$\text{CS}_2 + 3\text{O}_2 \rightarrow \text{CO}_2 + 2\text{SO}_2$

The heat of combustion is:
$\Delta H = \Delta H_1' + \Delta H_2' + \Delta H_3'$

$\Delta H = -117 - 393 - 594 = -1104\ \text{kJ mol}^{-1}$

Answer: $-1104\ \text{kJ mol}^{-1}$