Complete combustion of $0.858 \ g$ of compound $X$ gives $2.63 \ g$ of $CO_2$ and $1.28 \ g$ of $H_2O$. The lowest molecular mass $X$ can have is ............ $g$.

An organic compound has a molar mass of $108 \ g \ mol^{-1}$. The atoms $C, H,$ and $N$ are present in the weight ratio of $9 : 1 : 3.5$. What is the molecular formula of the compound?

$A$ certain compound has the molecular formula $X_4O_6$. If $10 \ g$ of $X_4O_6$ has $5.72 \ g$ of $X$,the atomic mass of $X$ is ............ $amu$.

$A$ carbon compound contains $12.8 \%$ of carbon,$2.1 \%$ of hydrogen and $85.1 \%$ of bromine. The molecular weight of the compound is $187.9$. Calculate the molecular formula of the compound. (Atomic weight: $H=1.008, C=12.0, Br=79.9$)

$A$ substance contains $38.8\% \ C$,$16.0\% \ H$,and $45.2\% \ N$. What is the empirical formula of the substance?

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.