The mole fraction of a solute in a 100 molal aqueous solution is ___________ $$\times$$ 10^$$-$$2. (Round off to the Nearest Integer).

[Given : Atomic masses : H : 1.0 u, O : 16.0 u ]

The standard enthalpies of formation of Al₂O₃ and CaO are $$-$$1675 kJ mol^-1 and $$-$$635 kJ mol^$$-$$1 respectively.

For the reaction

3CaO + 2Al $$ \to $$ 3Ca + Al₂O₃ the standard reaction enthalpy $$\Delta$$_rH⁰ = _________ kJ.

(Round off to the Nearest Integer)

The oxygen dissolved in water exerts a partial pressure of 20 kPa in the vapour above water. The molar solubility of oxygen in water is __________ $$\times$$ 10^$$-$$5 mol dm^$$-$$3. (Round off to the Nearest Integer).

[Given : Henry's law constant = K_H = 8.0 $$\times$$ 10⁴ kPa for O₂. Density of water with dissolved oxygen = 1.0 kg dm^$$-$$3 ]

In a triangle PQR, the co-ordinates of the points P and Q are ($$-$$2, 4) and (4, $$-$$2) respectively. If the equation of the perpendicular bisector of PR is 2x $$-$$ y + 2 = 0, then the centre of the circumcircle of the $$\Delta$$PQR is :