What is the chemical formula of rust?

Heating of carbonate ores in the absence of air to convert them into oxides is known as:

Describe ionic compounds on the basis of the following properties:
$(i)$ Strong force of attraction between positive and negative ions:
$(ii)$ Solubility of compounds in water.
$(iii)$ Electrical conductivity.

When finely powdered ore is placed on a rotating grooved table and rotated rapidly,the lighter impurities are removed. What is this method of concentration called?

What happens when a glass rod dipped in concentrated hydrochloric acid is brought near a container filled with ammonia gas?

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

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