Calculate change in enthalpy when 39 g acetylene is completely burnt with oxygen and enthalpy of combustion of acetylene is $$-$$1300 kJ/mol.

(At. mass C = 12, H = 1)

An ideal gas on isothermal reversible compression from 10L to 5L performs 1730J of work at 300 K. Calculate number of moles of gas involved in compression? (R = 8.314 J K$$^{-1}$$ mol$$^{-1}$$)

What is standard $N \equiv N$ bond enthalpy from following reaction,

$$\begin{aligned} & \mathrm{N}_2(g)+3 \mathrm{H}_2(g) \longrightarrow 2 \mathrm{NH}_3(g) ; \Delta H^{\circ}=-83 \mathrm{~kJ} \\ & \left(\Delta H^{\circ}(\mathrm{H}-\mathrm{H})=435 \mathrm{~kJ} ; \Delta H^{\circ}(\mathrm{N}-\mathrm{H})=389 \mathrm{~kJ}\right) \\ \end{aligned}$$

For the reaction,

$$\mathrm{N}_2(g)+3 \mathrm{H}_2(g) \longrightarrow 2 \mathrm{NH}_3(g) ; \Delta H$$

is equal to