Thermodynamics ...

A heat engine operating between 227 deg C and 27 deg C absorbs 1 kcal of heat from the 227 deg C reservoir per cycle. Calculate
(1) the amount of heat discharged into the low temperature reservoir.
(2) the amount of work done per cycle.
(3) the efficiency of cycle.

Calculate enthalpy for formation of ethylene from the following data:

What will be the heat formation of methane; if the heat of combustion of carbon is '$$-x$$' $$kJ$$, heat of formation of water is  '$$-y$$' $$kJ$$ and heat of combustion of methane is  '$$-z$$' $$kJ$$?

Which one of the following is not applicable for a thermochemical equation?

Super cooled water is liquid water that has been cooled below its normal freezing point. This state is thermodynamically :

If $${H}_{2}+\cfrac{1}{2}{O}_{2}\rightarrow {H}_{2}O;\Delta H=-68.09kcal$$
$$K+{H}_{2}O+water \rightarrow KOH(aq.)+\cfrac{1}{2}{H}_{2};\Delta H=-48.0kcal$$
$$KOH+water\rightarrow KOH(aq); \Delta H=-14.0kcal$$
the heat of formation of $$KOH$$ is:

$$S+{O}_{2}\rightarrow {SO}_{2}; \Delta H=-298.2kJ$$
$${ SO }_{ 2 }+\cfrac { 1 }{ 2 }{O}_{2} \rightarrow { SO_3 }; \Delta H=-98.7kJ$$
$${SO}_{3}+{H}_{2}O\rightarrow {H}_{2}{SO}_{4};\Delta H=-130.2kJ$$
$${H}_{2}+\cfrac { 1 }{ 2 } { O }_{ 2 }\rightarrow {H}_{2}O;\Delta H=-227.3kJ$$
The heat of formation of $${H}_{2}{SO}_{4}$$ will be:

$$\Delta {H}_{f(x)},\Delta {H}_{f(y)},\Delta {H}_{f(R)}$$ and $$\Delta {H}_{f(S)}$$ denote the enthalpies of formation of $$x,y,R$$ and $$S$$ respectively. The  enthalpy of the reaction $$x+y\rightarrow R+S$$ is:

Given that the bond energies of $$:N\equiv N$$ is $$946$$ kJ $$mol^{-1}$$ $$H-H$$ is $$435 $$ kJ $$mol^{-1}$$, $$N-N$$ is $$159$$ kJ $$mol^{-1}$$, and $$N-H$$ is $$389$$ kJ $$mol^{-1}$$, the heat of formation of hydrazine in the gas phase in kJ $$mol^{-1}$$ is: