Percentage of gold in $14$ carat gold is (in $\%$)

Which compound has the highest percentage of hydrogen by mass?

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

The molecular formula of potash alum is

$A$ compound contains $0.25\%$ of a metal with an atomic weight of $59$. If the compound contains one atom of the metal per molecule,what is the minimum molecular weight of the compound?

$A$ hydrocarbon contains $10.5 \, g$ of carbon and $1 \, g$ of hydrogen. If the volume of $2.4 \, g$ of this hydrocarbon is $1 \, L$ at $127 \, ^\circ C$ and $1 \, atm$ pressure,then the hydrocarbon is: