What is change in internal energy when system releases $$8 \mathrm{~kJ}$$ of heat and performs $$660 \mathrm{~J}$$ of work on the surrounding?

Calculate the final volume when 2 moles of an ideal gas expand from $$3 \mathrm{~dm}^3$$ at constant external pressure 1.6 bar and the work done in the process is $$800 \mathrm{~J}$$.

For $$\mathrm{NaCl}_{(\mathrm{s})}$$ enthalpy of solution is $$4 \mathrm{~kJ} \mathrm{~mol}^{-1}$$ and lattice enthalpy is $$790 \mathrm{~kJ} \mathrm{~mol}^{-1}$$. What is hydration enthalpy of $$\mathrm{NaCl}$$ ?

What is the value of $$\Delta H-\Delta U$$ for the following reaction?

$$2 \mathrm{C}_{(\mathrm{s})}+3 \mathrm{H}_{2(\mathrm{~g})} \rightarrow \mathrm{C}_2 \mathrm{H}_{6(\mathrm{~g})}$$