Match List - I with List - II.

List-I	List-II
A Concentration of gold ore	I Aniline
B Leaching of alumina	II NaOH
C Froth stabiliser	III $$SO_2$$
D Blister copper	IV NaCN

Choose the correct answer from the options given below

Let us match each item in List-I with the correct item in List-II.

A. Concentration of gold ore → IV (NaCN)

Gold ore is concentrated by the cyanide leaching process (MacArthur-Forrest process). Gold reacts with dilute NaCN solution in the presence of air to form a soluble gold cyanide complex:

$$4Au + 8NaCN + 2H_2O + O_2 \rightarrow 4Na[Au(CN)_2] + 4NaOH$$

B. Leaching of alumina → II (NaOH)

In Bayer's process, bauxite ore (containing $$Al_2O_3$$) is leached with concentrated NaOH solution. Alumina dissolves as sodium aluminate:

$$Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O$$

C. Froth stabiliser → I (Aniline)

In the froth floatation process, froth stabilisers like aniline or cresol are added to stabilise the froth so that the ore particles can be collected effectively.

D. Blister copper → III ($$SO_2$$)

Blister copper gets its name from the blisters formed on its surface due to the evolution of $$SO_2$$ gas during the solidification of molten copper. The $$SO_2$$ is produced during the bessemerisation process:

$$Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2$$

$$2Cu_2O + Cu_2S \rightarrow 6Cu + SO_2$$

The correct matching is: A-(IV), B-(II), C-(I), D-(III)

Hence, the correct answer is Option B.