The standard enthalpy of formation $(\Delta_f H^o_{298})$ for methane,$CH_4$ is $-74.9 \ kJ \ mol^{-1}$. In order to calculate the average energy given out in the formation of a $C-H$ bond from this,it is necessary to know which one of the following?

  • A
    The dissociation energy of the hydrogen molecule,$H_2$
  • B
    The first four ionisation energies of carbon.
  • C
    The dissociation energy of $H_2$ and enthalpy of sublimation of carbon (graphite).
  • D
    The first four ionisation energies of carbon and electron affinity of hydrogen.

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

Given $:$
$\Delta H^{\ominus}_{sub}[C(graphite)] = 710 \ kJ \ mol^{-1}$
$\Delta H^{\ominus}_{C-H} = 414 \ kJ \ mol^{-1}$
$\Delta H^{\ominus}_{H-H} = 436 \ kJ \ mol^{-1}$
$\Delta H^{\ominus}_{C=C} = 611 \ kJ \ mol^{-1}$
The $\Delta H^{\ominus}_{f}$ for $CH_2=CH_2$ is $............ \ kJ \ mol^{-1}$ $(nearest \ integer \ value)$

The enthalpy change for the reaction $2CO_{(g)} + O_{2(g)} \rightarrow 2CO_{2(g)}$ is known as:

Which of the following is an endothermic reaction?

$PbO$ exists in two crystalline forms: yellow and red. The standard enthalpies of formation for these two forms are $-217.3 \ kJ/mol$ and $-219.0 \ kJ/mol$,respectively. Calculate the enthalpy of transition for the process: $PbO \text{ (yellow)} \rightarrow PbO \text{ (red)}$ in $kJ/mol$.

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