"The resultant heat change in a reaction is the same whether it takes place in one or several stages." This statement is called

Three thermochemical equations are given below:
$(i) C_{(graphite)} + O_{2(g)} \to CO_{2(g)}; \Delta_r H^\circ = x \ kJ \ mol^{-1}$
$(ii) C_{(graphite)} + \frac{1}{2} O_{2(g)} \to CO_{(g)}; \Delta_r H^\circ = y \ kJ \ mol^{-1}$
$(iii) CO_{(g)} + \frac{1}{2} O_{2(g)} \to CO_{2(g)}; \Delta_r H^\circ = z \ kJ \ mol^{-1}$
Based on the above equations,find out which of the relationship given below is correct.

Given the thermochemical reactions:
$C(\text{graphite}) + \frac{1}{2} O_{2(g)} \to CO_{(g)}; \Delta H = -110.5 \ kJ$
$CO_{(g)} + \frac{1}{2} O_{2(g)} \to CO_{2(g)}; \Delta H = -283.2 \ kJ$
Calculate the heat of reaction for $C(\text{graphite}) + O_{2(g)} \to CO_{2(g)}$ in $kJ$.

The heat of combustion of solid benzoic acid at constant volume is $-321.30 \ kJ$ at $27^{\circ} C$. The heat of combustion at constant pressure is $(-321.30 - x R) \ kJ$. The value of $x$ is . . . . . . .

What will be the $C-H$ bond enthalpy if:
$CH_{4(g)} + 2O_{2(g)} \rightarrow CO_{2(g)} + 2H_2O_{(l)};$ $\Delta H = -890 \, kJ$
$CO_{2(g)} \rightarrow C_{(graphite)} + O_{2(g)};$ $\Delta H = 393 \, kJ$
$2H_2O_{(l)} \rightarrow 2H_{2(g)} + O_{2(g)};$ $\Delta H = 571 \, kJ$
$2H_{2(g)} \rightarrow 4H_{(g)};$ $\Delta H = 871 \, kJ$
$C_{(graphite)} \rightarrow C_{(g)};$ $\Delta H = 716 \, kJ$

For the reaction $Cl_{2(g)} \rightarrow 2Cl_{(g)}$,the value of $\Delta H$ is .......