If $1.24 \ g$ of $P$ is present in a $2.2 \ g$ sample of a compound,identify the empirical formula of the compound (Atomic mass of $P = 31 \ g/mol$,$S = 32 \ g/mol$).

$120 \ g$ of an organic compound that contains only carbon and hydrogen gives $330 \ g$ of $CO_{2}$ and $270 \ g$ of water on complete combustion. The percentage of carbon and hydrogen,respectively,are ...... .

Reduction of $7.2 \, g$ of a metal oxide yields $6.4 \, g$ of the metal. If the atomic mass of the metal is $128 \, g/mol$,the formula of the oxide is .....

If two compounds have the same empirical formula but different molecular formulae,they must have:

In $CH_3CH_2Br$,the percentage of $Br$ is:

$0.30 \ g$ of an organic compound containing $C$,$H$ and $O$ on combustion yields $0.44 \ g \ CO_2$ and $0.18 \ g \ H_2O$. If $1 \ mol$ of the compound weighs $60 \ g$,then the molecular formula of the compound is: