If at $298 \, K$ the bond energies of $C-H, C-C, C=C$ and $H-H$ bonds are respectively $414, 347, 615$ and $435 \, kJ \, mol^{-1}$,the value of enthalpy change for the reaction $H_2C=CH_{2(g)} + H_{2(g)} \to H_3C-CH_{3(g)}$ at $298 \, K$ will be $.... \, kJ$.

The heat of combustion of a substance is:

The enthalpies of combustion of diamond and graphite are $-395.4 \, kJ$ and $-393.5 \, kJ$ respectively. The enthalpy of transformation of diamond to graphite is ..... $kJ$.

For strong acid and strong base neutralisation,the net chemical change is $H^{+} + OH^{-} \longrightarrow H_2O_{(l)}$; $\Delta_r H^{\circ} = -55.84 \ kJ \ mol^{-1}$. If the enthalpy of neutralisation of $CH_3COOH$ by $NaOH$ is $-49.86 \ kJ \ mol^{-1}$,then the enthalpy of ionisation of $CH_3COOH$ is:

The following thermochemical reactions are given:
$M + \frac{1}{2} O_2 \to MO + 351.4 \ kJ$ $(i)$
$X + \frac{1}{2} O_2 \to XO + 90.8 \ kJ$ $(ii)$
It follows that the heat of reaction for the following process $M + XO \rightleftharpoons MO + X$ is given by $... \ kJ$.

The total enthalpy change in a chemical reaction is equal to the algebraic sum of the enthalpy changes of the individual steps of the reaction. This statement is associated with which scientist?