Match List-$I$ with List-$II$.

List-$I$ (Industrial process)	List-$II$ (Application)
$(a)$ Haber's process	$(i)$ $HNO_{3}$ synthesis
$(b)$ Ostwald's process	$(ii)$ Aluminium extraction
$(c)$ Contact process	$(iii)$ $NH_{3}$ synthesis
$(d)$ Hall-Heroult process	$(iv)$ $H_{2}SO_{4}$ synthesis

Choose the correct answer from the options given below:

Concentrated sodium hydroxide can separate a mixture of

Addition of high proportions of manganese makes steel useful in making rails of rail-roads because manganese

Consider the following metallurgical processes:
$I$. Heating impure metal with $CO$ and distilling the resulting volatile carbonyl (b.p. $43 \ ^oC$) and finally decomposition at $150 \ ^oC - 200 \ ^oC$ to get the pure metal.
$II$. Heating the sulphide ore in air until a part is converted to oxide and then further heating in the absence of air to let the oxide react with unchanged metal sulphide.
$III$. Electrolysis of the molten electrolyte containing approximately equal amounts of the metal chloride and $NaCl$ to obtain the metal.
The processes used for obtaining magnesium,nickel and copper are respectively:

Identify the products of the reaction: $4FeCr_2O_4 + 8Na_2CO_3 + 7O_2 \rightarrow ?$

What is known as Thomas slag?