In $CH_3CH_2Br$,the percentage of $Br$ is:

$A$ metal $M$ sulfate contains $9.87 \% \, M$. If it is isomorphous with $ZnSO_4 \cdot 7H_2O$,what is the atomic mass of $M$ (in $.3$)?

An organic compound is estimated through the Dumas method and is found to evolve $6$ moles of $CO_2$,$4$ moles of $H_2O$,and $1$ mole of nitrogen gas. The formula of the compound is

What is the percentage by mass of oxygen in $NaOH$? (Atomic mass of $Na=23 \ u, O=16 \ u, H=1 \ u$)

$A$ compound $X$ contains $32 \%$ of $A$,$20 \%$ of $B$,and the remaining percentage of $C$. Then,the empirical formula of $X$ is:
(Given atomic masses of $A = 64$,$B = 40$,$C = 32 \ u$)

$925$ fine silver means an alloy of :