The heats of combustion of rhombic and monoclinic sulphur are respectively $70960 \ cal$ and $71030 \ cal$. What will be the heat of conversion of rhombic sulphur to monoclinic? $(cal)$

What do you understand by exothermic reaction and endothermic reaction? Give one example of each type.

Consider the reactions:
$C_{(s)} + 2H_{2(g)} \to CH_{4(g)}, \Delta H = -x \ kcal$
$C_{(g)} + 4H_{(g)} \to CH_{4(g)}, \Delta H = -x_1 \ kcal$
$CH_{4(g)} \to CH_{3(g)} + H_{(g)}, \Delta H = +y \ kcal$
The bond energy of $C-H$ bond is:

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 standard enthalpy of formation of $NH_3$ is $-46.0 \, kJ \, mol^{-1}$. If the enthalpy of atomization of $H_2$ is $436 \, kJ \, mol^{-1}$ and that of $N_2$ is $712 \, kJ \, mol^{-1}$,what is the average bond enthalpy of the $N-H$ bond in $NH_3$ in $kJ \, mol^{-1}$?

The standard enthalpies of formation of $CO$ and $CO_2$ are $-110 \, kJ \, mol^{-1}$ and $-394 \, kJ \, mol^{-1}$ respectively. What will be the heat of combustion of $1 \, mol$ of graphite in $kJ$?