The acidic character of the group-$15$ elements' oxides in increasing order is:

When tin is treated with concentrated nitric acid,what is the product formed?

$PH_3$ forms bubbles when passed slowly in water but $NH_3$ dissolves. Explain why?

Which of the following statements are correct about the reaction between the copper metal and dilute $HNO_3$?
$(I)$ The principal reducing product is $NO$ gas.
$(II)$ $Cu$ metal is oxidised to $Cu^{2+}$ (aq.) ion which is blue in colour.
$(III)$ $NO$ is paramagnetic and has one unpaired electron in antibonding molecular orbital.
$(IV)$ $NO$ reacts with $O_2$ to produce $NO_2$ which is linear in shape.
Choose the correct statements.

What are $X$ and $Y$,respectively in the following reactions?
$Au + \text{aqua regia} \longrightarrow AuCl_4^{-} + H_2O + X$
$Pt + \text{aqua regia} \longrightarrow PtCl_6^{2-} + H_2O + Y$

An orange solid $(X)$ on heating,gives a colourless gas $(Y)$ and a green residue $(Z).$ Gas $(Y)$ on treatment with $Mg,$ produces a white solid substance. Identify the white solid substance.