Using the equations below:

$$\begin{array}{*{20}{l}} {{\text{C(s)}} + {{\text{O}}_{\text{2}}}{\text{(g)}} \to {\text{C}}{{\text{O}}_{\text{2}}}{\text{(g)}}}&{\Delta {H^\Theta } =  - 390{\text{ kJ}}} \\ {{{\text{H}}_2}{\text{(g)}} + \frac{1}{2}{{\text{O}}_2}{\text{(g)}} \to {{\text{H}}_2}{\text{O(l)}}}&{\Delta {H^\Theta } =  - 286{\text{ kJ}}} \\ {{\text{C}}{{\text{H}}_4}{\text{(g)}} + {\text{2}}{{\text{O}}_2}{\text{(g)}} \to {\text{C}}{{\text{O}}_2}{\text{(g)}} + {\text{2}}{{\text{H}}_2}{\text{O(l)}}}&{\Delta {H^\Theta } =  - 890{\text{ kJ}}} \end{array}$$

what is ${\Delta {H^\Theta }}$, in kJ, for the following reaction?

$${\text{ C(s)}} + {\text{2}}{{\text{H}}_2}{\text{(g)}} \to {\text{C}}{{\text{H}}_4}{\text{(g)}}$$

A.     –214

B.     –72

C.     +72

D.     +214

B

The examination normally uses kJ when an equation is given as here; if it were to quote a value, say, for the heat of formation of a compound, then this would be given in kJ$\,$mol^–1.