$$1.0 \mathrm{~g}$$ of $$\mathrm{H}_2$$ has same number of molecules as in:

On complete combustion, 0.3 g of an organic compound gave 0.2 g of CO$$_2$$ and 0.1 g of H$$_2$$O. The percentage composition of carbon and hydrogen in the compound, respectively is:

1 gram of sodium hydroxide was treated with $$25 \mathrm{~mL}$$ of $$0.75 \mathrm{~M} \mathrm{~HCl}$$ solution, the mass of sodium hydroxide left unreacted is equal to

The highest number of helium atoms is in