The empirical formula of a compound is $CH_2O$ and its molecular mass is $90$. The molecular formula of the compound is:

An organic compound with a molecular weight of $60$ contains $C = 20\%$,$H = 6.67\%$,and $N = 46.67\%$,with the remainder being oxygen. Upon heating,the solid residue gives a violet color with alkaline copper sulfate solution. Identify the compound.

$A$ hydrocarbon contains $85.7 \% C$. If $42 \, mg$ of the compound contains $3.01 \times 10^{20}$ molecules,the molecular formula of the compound will be

$2.0 \text{ g}$ of a bromo hydrocarbon $(X)$ was subjected to Carius analysis,which gave $3.36 \text{ g}$ of $AgBr$. The percentage of carbon in the compound $(X)$ is $26.7\%$. The total number of carbon atoms in the empirical formula for compound $(X)$ is . . . . . . .

Chlorophyll,the green pigment in plants responsible for photosynthesis,contains $2.68\%$ of magnesium by mass. Calculate the number of magnesium atoms in $2.00 \ g$ of chlorophyll.

$A$ compound contains $4.07\%$ hydrogen,$24.27\%$ carbon,and $71.65\%$ chlorine. Its molar mass is $98.96\ g/mol$. What are its empirical and molecular formulas?