An aqueous solution of alcohol contains $$18 \mathrm{~g}$$ of water and $$414 \mathrm{~g}$$ of ethyl alcohol. The mole fraction of water is

A pure compound contains $$2.4 \mathrm{~g}$$ of $$\mathrm{C}, 1.2 \times 10^{23}$$ atoms of $$\mathrm{H}, 0.2$$ moles of oxygen atoms. Its empirical formula is

$$0.4 \mathrm{~g}$$ of dihydrogen is made to react with $$7.4 \mathrm{~g}$$ of dichlorine to form hydrogen chloride. The volume of hydrogen chloride formed at $$273 \mathrm{~K}$$ and $$1 \mathrm{~bar}$$ pressure is

A gas mixture contains $$25 \% \mathrm{~He}$$ and $$75 \% \mathrm{~CH}_4$$ by volume at a given temperature and pressure. The percentage by mass of methane in the mixture is approximately _________.