Bleaching powder is correctly represented as

Match List-$I$ with List-$II$ for the compositions of substances and select the correct answer using the codes given below.

List-$I$ (Substances)	List-$II$ (Composition)
$A$. Plaster of Paris	$i$. $CaSO_4 \cdot \frac{1}{2} H_2O$
$B$. Epsomite	$ii$. $MgSO_4 \cdot 7H_2O$
$C$. Kieserite	$iii$. $MgSO_4 \cdot H_2O$
$D$. Gypsum	$iv$. $CaSO_4 \cdot 2H_2O$
	$v$. $CaSO_4$

The number of electrons and protons in the third alkaline earth metal ion $(Ca^{2+})$ will be:

$A$ solid compound $X$ on heating gives $CO_2$ gas and a residue. The residue mixed with water forms compound $Y$. On passing excess $CO_2$ gas through $Y$,a clear solution $Z$ is formed. On heating $Z$,compound $X$ is recovered. What is compound $X$?
$\mathop X\limits_{solid}$ $\xrightarrow{\text{heating}} CO_2 + \text{residue}$ $\xrightarrow{H_2O} Y$ $\xrightarrow{\text{excess } CO_2} \mathop Z\limits_{\text{solution}}$ $\xrightarrow{\text{heating}} X$

$A$ mixture of $MgCl_2$ and $MgO$ is called

Give two uses of beryllium and magnesium.