The cyanamide process is used in the formation of:

Arrange the following oxides in the correct order of their acidic character:
$N_2O_3$ $(I)$,$P_2O_3$ $(II)$,$N_2O_5$ $(III)$,$As_2O_3$ $(IV)$

Choose the correct statement$(s)$ among the following.
$A$. $SnCl_2 \cdot 2 H_2O$ is a reducing agent.
$B$. $SnO_2$ reacts with $KOH$ to form $K_2[Sn(OH)_6]$.
$C$. $A$ solution of $PbCl_2$ in $HCl$ contains $Pb^{2+}$ and $Cl^{-}$ ions.
$D$. The reaction of $Pb_3O_4$ with hot dilute nitric acid to give $PbO_2$ is a redox reaction.

Which of the following represents the correct order of acidic strength?

When $PbO_2$ reacts with concentrated $HNO_3$,the evolved gas is:

The number of hydrogen atom$(s)$ attached directly to the phosphorus atom in hypophosphorous acid $(H_3PO_2)$ is: