On reduction with hydrogen,$3.6 \ g$ of an oxide of metal $(M)$ left $3.2 \ g$ of the metal. If the atomic weight of the metal is $64$,the formula of the oxide is:

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 $(C_6H_5Cl)$

$A$ pure compound contains $2.4 \ g$ of $C$,$1.2 \times 10^{23}$ atoms of $H$,and $0.2 \ mol$ of oxygen atoms. Its empirical formula is

$0.30 \ g$ of an organic compound containing $C$,$H$ and $O$ on combustion yields $0.44 \ g \ CO_2$ and $0.18 \ g \ H_2O$. If $1 \ mol$ of the compound weighs $60 \ g$,then the molecular formula of the compound is:

The empirical formula of a compound is $CH_2O$. If its molecular weight is $180$,what is the molecular formula of the compound?

Calculate the mass percent of calcium,phosphorus,and oxygen in calcium phosphate $Ca_{3}(PO_{4})_{2}$.