The number of atoms in 8g of sodium is x $$\times$$ 10²³. The value of x is ____________. (Nearest integer)

[Given : N_A = 6.02 $$\times$$ 10²³ mol^$$-$$1

Atomic mass of Na = 23.0 u]

If 80 g of copper sulphate CuSO₄ . 5H₂O is dissolved in deionised water to make 5L of solution. The concentration of the copper sulphate solution is x $$\times$$ 10^$$-$$3 mol L^$$-$$1. The value of x is _____________.

[Atomic masses Cu : 63.54u, S : 32u, O : 16u, H : 1u]

Sodium oxide reacts with water to produce sodium hydroxide. 20.0 g of sodium oxide is dissolved in 500 mL of water. Neglecting the change in volume, the concentration of the resulting NaOH solution is ______________ $$\times$$ 10^$$-$$1 M. (Nearest integer) [Atomic mass : Na = 23.0, O = 16.0, H = 1.0]

The molarity of the solution prepared by dissolving 6.3 g of oxalic acid (H₂C₂O₄.2H₂O) in 250 mL of water in mol L^$$-$$1 is x $$\times$$ 10^$$-$$2. The value of x is _____________. (Nearest integer) [Atomic mass : H : 1.0, C : 12.0, O : 16.0]