Make the correct pairs from below mentioned $'X'$ and $'Y':$

$1. \text{Sulphurous acid}$	$p. H_{3}PO_{4}$
$2. \text{Sulphuric acid}$	$q. H_{2}S_{2}O_{7}$
$3. \text{Oleum}$	$r. H_{2}SO_{3}$
$4. \text{Phosphoric acid}$	$s. H_{2}SO_{4}$

What is the percentage concentration of sodium hydroxide solution used in the Bayer process (in $\%$)?

Which metal oxide cannot be reduced by carbon?

What is formed when sulfur trioxide gas is absorbed in concentrated sulfuric acid?

Silver articles become black on prolonged exposure to air. This is due to the formation of:

$A$ metal $E$ is stored under kerosene oil. When a small piece of it is left open in the air,it catches fire. When the product formed is dissolved in water,it turns red litmus blue.
$(i)$ Name the metal $E$.
$(ii)$ Write the chemical equations for the reaction when it is exposed to air and when the product is dissolved in water.
$(iii)$ Explain the process by which the metal is obtained from its molten chloride.