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)

A $$100 \mathrm{~mL}$$ solution of $$\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{MgBr}$$ on treatment with methanol produces $$2.24 \mathrm{~mL}$$ of a gas at STP. The weight of gas produced is _____________ mg. [nearest integer]

Chlorophyll extracted from the crushed green leaves was dissolved in water to make $$2 \mathrm{~L}$$ solution of Mg of concentration $$48\, \mathrm{ppm}$$. The number of atoms of $$\mathrm{Mg}$$ in this solution is $$x \times 10^{20}$$ atoms. The value of $$x$$ is ___________. (Nearest Integer)

(Given : Atomic mass of $$\mathrm{Mg}$$ is $$24 \mathrm{~g} \mathrm{~mol}^{-1} ; \mathrm{N}_{\mathrm{A}}=6.02 \times 10^{23} \mathrm{~mol}^{-1}$$ )