For a given chemical reaction A $$\to$$ B at 300 K the free energy change is $$-$$49.4 kJ mol^$$-$$1 and the enthalpy of reaction is 51.4 kJ mol^$$-$$1. The entropy change of the reaction is _____________ JK^$$-$$1 mol^$$-$$1.

The wavelength of electrons accelerated from rest through a potential difference of 40 kV is x $$\times$$ 10^$$-$$12 m. The value of x is ___________. (Nearest integer)

Give : Mass of electron = 9.1 $$\times$$ 10^$$-$$31 kg

Charge on an electron = 1.6 $$\times$$ 10^$$-$$19 C

Planck's constant = 6.63 $$\times$$ 10^$$-$$34 Js

The vapour pressures of A and B at 25$$^\circ$$C are 90 mm Hg and 15 mm Hg respectively. If A and B are mixed such that the mole fraction of A in the mixture is 0.6, then the mole fraction of B in the vapour phase is x $$\times$$ 10^$$-$$1. The value of x is ___________. (Nearest integer)

4g equimolar mixture of NaOH and Na₂CO₃ contains x g of NaOH and y g of Na₂CO₃. The value of x is ____________ g. (Nearest integer)