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

$A$ compound has an empirical formula $C_2H_4O$. An independent analysis gave a value of $132.16$ for its molecular mass. What is the correct molecular formula?

Arrange the following compounds in the increasing order of percentage of chlorine by weight:
$I.$ $DDT$ $(C_{14}H_9Cl_5)$
$II.$ Gammaxene $(C_6H_6Cl_6)$
$III.$ Carbon tetrachloride $(CCl_4)$
$IV.$ Chlorobenzene $(C_6H_5Cl)$

An organic compound contains $C$,$H$ and $S$. The minimum molecular weight of the compound containing $8\%$ sulphur is........$g\,mol^{-1}$ (atomic weight of $S = 32\,amu$)

$A$ compound contains $8\%$ sulfur by weight. The minimum molecular weight of the compound is:

$A$ sample of calcium carbonate $(CaCO_3)$ has the following percentage composition: $Ca = 40\%$; $C = 12\%$; $O = 48\%$. If the law of constant proportions is true,then the weight of calcium in $4 \, g$ of a sample of calcium carbonate obtained from another source will be $... \, g$.