When 5 moles of He gas expand isothermally and reversibly at 300 K from 10 litre to 20 litre, the magnitude of the maximum work obtained is __________ J. [nearest integer] (Given : R = 8.3 J K^$$-$$1 mol^$$-$$1 and log 2 = 0.3010)

A solution containing 2.5 $$\times$$ 10^$$-$$3 kg of a solute dissolved in 75 $$\times$$ 10^$$-$$3 kg of water boils at 373.535 K. The molar mass of the solute is ____________ g mol^$$-$$1. [nearest integer] (Given : K_b(H₂O) = 0.52 K kg mol^$$-$$1 and boiling point of water = 373.15 K)

pH value of 0.001 M NaOH solution is ____________.

For the reaction taking place in the cell :

Pt (s)| H₂ (g)|H⁺(aq) || Ag⁺(aq) |Ag (s)

E$$_{cell}^o$$ = + 0.5332 V.

The value of $$\Delta$$_fG$$^\circ$$ is ______________ kJ mol^$$-$$1. (in nearest integer)