2L of 0.2M H₂SO₄ is reacted with 2L of 0.1M NaOH solution, the molarity of the resulting product Na₂SO₄ in the solution is _________ millimolar. (Nearest integer)

In the given reaction,

$$X+Y+3 Z \leftrightarrows X YZ_{3}$$

if one mole of each of $$X$$ and $$Y$$ with $$0.05 \mathrm{~mol}$$ of $$Z$$ gives compound $$X Y Z_{3}$$. (Given : Atomic masses of $$X, Y$$ and $$Z$$ are 10, 20 and 30 amu, respectively.) The yield of $$X YZ_{3}$$ is _____________ g. (Nearest integer)

On complete combustion of $$0.492 \mathrm{~g}$$ of an organic compound containing $$\mathrm{C}, \mathrm{H}$$ and $$\mathrm{O}$$, $$0.7938 \mathrm{~g}$$ of $$\mathrm{CO}_{2}$$ and $$0.4428 \mathrm{~g}$$ of $$\mathrm{H}_{2} \mathrm{O}$$ was produced. The % composition of oxygen in the compound is ___________.

$$20 \mathrm{~mL}$$ of $$0.02 \,\mathrm{M} \,\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$$ solution is used for the titration of $$10 \mathrm{~mL}$$ of $$\mathrm{Fe}^{2+}$$ solution in the acidic medium.

The molarity of $$\mathrm{Fe}^{2+}$$ solution is __________ $$\times \,10^{-2}\, \mathrm{M}$$. (Nearest Integer)