$4 \ g$ of a hydrocarbon on complete combustion gave $12.571 \ g$ of $CO_2$ and $5.143 \ g$ of water. What is the empirical formula of the hydrocarbon?

An organic compound has an empirical formula of $CH_2O$ and a molecular mass of $90$. What is its molecular formula? $(C = 12, H = 1, O = 16)$

$A$ 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?

Find the empirical formula of an organic compound if it contains $18.6 \% C$,$1.55 \% H$,and $55.04 \% Cl$. (Atomic masses: $C=12$,$H=1$,$Cl=35.5$,$O=16$)

An organic compound contains carbon,hydrogen,and oxygen with percentages of $38.71\%$,$9.67\%$,and $51.62\%$ respectively. Determine the empirical formula of this compound.

$A$ sample of a hydrate of barium chloride weighing $61 \ g$ was heated until all the water of hydration was removed. The dried sample weight is $52 \ g$. The formula of the hydrated salt is: (atomic mass: $Ba = 137 \ amu, Cl = 35.5 \ amu$)