Which of the following compounds has a standard molar enthalpy of formation equal to zero at $298 \ K$?

Explain Enthalpy of atomization $\left( \Delta_{a} H^{\theta} \right)$.

Heat of transition is the heat evolved or absorbed when a substance is converted from

Calculate the enthalpy of formation of ethylene $(C_2H_4)$ from the following data:
$I. C_{(graphite)} + O_{2(g)} \rightarrow CO_{2(g)}; \Delta H = -393.5 \ kJ$
$II. H_{2(g)} + \frac{1}{2}O_{2(g)} \rightarrow H_2O_{(l)}; \Delta H = -286.2 \ kJ$
$III. C_2H_{4(g)} + 3O_{2(g)} \rightarrow 2CO_{2(g)} + 2H_2O_{(l)}; \Delta H = -1410.8 \ kJ$ (in $kJ$)

Which of these species has a standard enthalpy of formation equal to zero?

If the enthalpy change during the combustion of benzene is $-3264.6 \ kJ/mol$,then the heat produced by the combustion of $39 \ g$ of benzene is ...... $kJ$.