Combustion of 1 mole of benzene is expressed at

$$\mathrm{C}_6 \mathrm{H}_6(\mathrm{l})+\frac{15}{2} \mathrm{O}_2(\mathrm{~g}) \rightarrow 6 \mathrm{CO}_2(\mathrm{~g})+3 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \text {. }$$

The standard enthalpy of combustion of $$2 \mathrm{~mol}$$ of benzene is $$-^{\prime} x^{\prime} \mathrm{kJ}$$. $$x=$$ __________.

Given :

1. standard Enthalpy of formation of $$1 \mathrm{~mol}$$ of $$\mathrm{C}_6 \mathrm{H}_6(\mathrm{l})$$, for the reaction $$6 \mathrm{C}$$ (graphite) $$+3 \mathrm{H}_2(\mathrm{g}) \rightarrow \mathrm{C}_6 \mathrm{H}_6(\mathrm{l})$$ is $$48.5 \mathrm{~kJ} \mathrm{~mol}^{-1}$$.

2. Standard Enthalpy of formation of $$1 \mathrm{~mol}$$ of $$\mathrm{CO}_2(\mathrm{g})$$, for the reaction $$\mathrm{C}$$ (graphite) $$+\mathrm{O}_2(\mathrm{g}) \rightarrow \mathrm{CO}_2(\mathrm{g})$$ is $$-393.5 \mathrm{~kJ} \mathrm{~mol}^{-1}$$.

3. Standard and Enthalpy of formation of $$1 \mathrm{~mol}$$ of $$\mathrm{H}_2 \mathrm{O}(\mathrm{l})$$, for the reaction $$\mathrm{H}_2(\mathrm{g})+\frac{1}{2} \mathrm{O}_2(\mathrm{g}) \rightarrow \mathrm{H}_2 \mathrm{O}(\mathrm{l})$$ is $$-286 \mathrm{~kJ} \mathrm{~mol}^{-1}$$.

The heat of combustion of solid benzoic acid at constant volume is $$-321.30 \mathrm{~kJ}$$ at $$27^{\circ} \mathrm{C}$$. The heat of combustion at constant pressure is $$(-321.30-x \mathrm{R}) \mathrm{~kJ}$$, the value of $$x$$ is __________.

Three moles of an ideal gas are compressed isothermally from $$60 \mathrm{~L}$$ to $$20 \mathrm{~L}$$ using constant pressure of $$5 \mathrm{~atm}$$. Heat exchange $$\mathrm{Q}$$ for the compression is - _________ Lit. atm.

The enthalpy of formation of ethane $$(\mathrm{C}_2 \mathrm{H}_6)$$ from ethylene by addition of hydrogen where the bond-energies of $$\mathrm{C}-\mathrm{H}, \mathrm{C}-\mathrm{C}, \mathrm{C}=\mathrm{C}, \mathrm{H}-\mathrm{H}$$ are $$414 \mathrm{~kJ}, 347 \mathrm{~kJ}, 615 \mathrm{~kJ}$$ and $$435 \mathrm{~kJ}$$ respectively is $$-$$ __________ $$\mathrm{kJ}$$