Arrange the acids $(I)$ $H_2SO_3$,$(II)$ $H_3PO_3$,and $(III)$ $HClO_3$ in the decreasing order of acidity.

In view of the signs of $\Delta_{r} G^{\circ}$ for the following reactions:
$PbO_2 + Pb \longrightarrow 2 PbO, \Delta_{r} G^{\circ} < 0$
$SnO_2 + Sn \longrightarrow 2 SnO, \Delta_{r} G^{\circ} > 0$
Which oxidation states are more characteristic for lead and tin?

If the valency of $A$ is $3$ and $B$ is $2$,then the formula of the compound formed is:

Carbon has a valency of $2$ in $CO$ and $4$ in $CO_2$ and $CH_4$. Its valency in acetylene $(C_2H_2)$ is

Assertion : $HClO_4$ is a stronger acid than $HClO_3$.
Reason : Oxidation state of $Cl$ in $HClO_4$ is $+VII$ and in $HClO_3$ is $+V$.

The general formula of the compound formed when a metal $(M)$ of group $1$ reacts with a non-metal $(X)$ of group $16$ is: