4.0 L of an ideal gas is allowed to expand isothermally into vacuum until the total volume is 2.0 L. The amount of heat absorbed in this expansion is ____________ L atm.

The vapour pressures of two volatile liquids A and B at 25$$^\circ$$C are 50 Torr and 100 Torr, respectively. If the liquid mixture contains 0.3 mole fraction of A, then the mole fraction of liquid B in the vapour phase is $${x \over {17}}$$. The value of x is ______________.

The solubility product of a sparingly soluble salt A₂X₃ is 1.1 $$\times$$ 10^$$-$$23. If specific conductance of the solution is 3 $$\times$$ 10^$$-$$5 S m^$$-$$1, the limiting molar conductivity of the solution is $$x \,\times$$ 10^$$-$$3 S m² mol^$$-$$1. The value of x is ___________.

The quantity of electricity in Faraday needed to reduce 1 mol of Cr₂O$$_7^{2 - }$$ to Cr³⁺ is ____________.