$A$ metal oxide contains $75 \%$ metal by mass. If the vapour density of the metal chloride is $89$,what is the atomic weight of the metal?

The ratio of the number of water molecules in Mohr's salt and potash alum is $.... \times 10^{-1}$.

Match List-$I$ with List-$II$ and select the correct option (Based on mole concept):

List-$I$	List-$II$
$(a)$ $2 \text{ moles of ethene}$	$(i)$ $11.2 \text{ L volume at STP}$
$(b)$ $\text{Molar mass is equal to } 66 \text{ g}$	$(ii)$ $56 \text{ g}$
$(c)$ $1 \text{ g of } H_2$	$(iii)$ $12.04 \times 10^{23} \text{ molecules}$
$(d)$ $2 \text{ moles of water vapours}$	$(iv)$ $1.5 \text{ mole of } CO_2$

If $2.4088 \times 10^{21}$ molecules are removed from $392 \, mg$ of $H_2SO_4$ in a container,the number of $H_2SO_4$ molecules remaining in the container will be ........

The incorrect postulates of the Dalton's atomic theory are :
$A$. Atoms of different elements differ in mass.
$B$. Matter consists of divisible atoms.
$C$. Compounds are formed when atoms of different element combine in a fixed ratio.
$D$. All the atoms of given element have different properties including mass.
$E$. Chemical reactions involve reorganisation of atoms.
Choose the correct answer from the options given below :

When a standard solution of $NaOH$ is left in air for a few hours: