What is the value of temperature in degree Celsius at absolute zero ?

Calculate the work done when 2 moles of an ideal gas expand from a volume of $$5 \mathrm{~dm}^3$$ to $$7 \times 10^{-3} \mathrm{~m}^3$$ against a constant external pressure of $$2.02 \times 10^5 \mathrm{~Nm}^{-2}$$ ?

What is the heat of formation of $$\mathrm{HCl}_{(\mathrm{g})}$$ from following equation?

$$\mathrm{H}_{2(\mathrm{~g})}+\mathrm{Cl}_{2(\mathrm{g})} \rightarrow 2 \mathrm{HCl}_{(\mathrm{g})} \Delta_{\mathrm{f}} \mathrm{H}=-194 \mathrm{~kJ}$$

If $$\mathrm{Q}$$ is the heat liberated from the system and $$\mathrm{W}$$ is the work done on the system then first law of thermodynamics can be written as,