Principles of Metallurgy — Practice

Question 1

The impurity present in the ore is called

Accepted Answer

Gangue

Question 2

Which of the following is a carbonate ore?

Accepted Answer

Magnesite

Question 3

Which of the following is the correct formula of gypsum?

Accepted Answer

CaSO4.2H2O

Question 4

The oil used in the froth flotation process is

Accepted Answer

pine oil

Question 5

Froth flotation is a method used for the concentration of which type of ore?

Accepted Answer

sulphide

Question 6

Galena is an ore of

Accepted Answer

Pb

Question 7

The metal that occurs in the native form is

Accepted Answer

Au

Question 8

The most abundant metal in the earth's crust is

Accepted Answer

Aluminium

Question 9

The reducing agent in the thermite process is

Accepted Answer

Al

Question 10

The purpose of smelting an ore is to

Accepted Answer

Reduce

Question 11

Magnesium is an active metal. If it occurs as a chloride in nature, which method of reduction is suitable for its extraction?

Accepted Answer

Electrolysis of the fused (molten) magnesium chloride.

Question 12

What is the difference between roasting and calcination? Give one example of each.

Accepted Answer

Roasting is heating the ore strongly in the presence of air or oxygen, used for sulphide ores: 2ZnS + 3O2 -> 2ZnO + 2SO2. Calcination is heating the ore in the absence of air, used for carbonate ores, which decompose: CaCO3 -> CaO + CO2.

Question 13

When do we use the magnetic separation method for concentration of an ore? Explain with an example.

Accepted Answer

When either the ore or the impurity is magnetic and the other is not. The powdered ore is carried on a moving belt that passes between a magnetic wheel and a non-magnetic wheel; the magnetic material is attracted and falls in a separate heap.

Question 14

Mention two methods which produce very pure metals from impure metals.

Accepted Answer

Electrolytic refining and distillation.

Question 15

Explain the thermite process and mention its applications in daily life.

Accepted Answer

The thermite process is the reduction of a metal oxide by aluminium. Fe2O3 + 2Al -> Al2O3 + 2Fe + heat, and similarly Cr2O3 + 2Al -> Al2O3 + 2Cr + heat. Aluminium is more reactive than iron or chromium, so it displaces them from their oxides. The reaction is so highly exothermic that the metal produced is in the molten state. The molten iron it yields is used to join the railings of railway tracks and to repair cracked machine parts.

Question 16

Suggest an experiment to prove that the presence of both air and water is essential for corrosion, and explain the procedure.

Accepted Answer

Take three test tubes A, B and C and place clean iron nails in each. In A pour some water and cork it, so the nails meet both air and water. In B pour boiled distilled water, add about 1 ml of oil and cork it; the oil floats and prevents air from dissolving, so the nails meet water but no air. In C put some anhydrous calcium chloride and cork it; it absorbs any moisture, so the nails meet dry air but no water. Leave them for a few days. The nails rust only in A, showing that both air and water are needed.

Practice — Principles of Metallurgy

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