101.

Heat treatment alters the properties of steel due to

• chemical reaction on heating

• partial rusting

• change in the residual energy

• change in the lattice structure due to differential rate of cooling

Match List-I withList-II and select the correct answer using the codes given below.

Codes

• A  B  C  D

  1  3  4   2

• A  B  C  D

  3   1  2  4

• A  B  C  D

  2  1   4  3

• A  B  C  D

  1  2   3  4

In Goldschmidt aluminothermic process, thermite contains

• 3 parts of Al₂O₃ and 4 parts of Al

• 3 parts of Fe₂O₃ and 2 parts of Al

• 3 parts of Fe₂O₃ and 1 part of Al

• 1 part of Fe₂O₃ ad 1 part of Al

In the electrolytic method of obtaining aluminium from purified bauxite, cryolite is added to the charge in order to

• minimise the heat loss due to radiation

• protect aluminium produced from oxygen

• dissolve bauxite and render it conductor of electricity

• lower the melting point of bauxite.

Identify the reaction that does not take place during the smelting process of copper extraction

• 2FeS + 3O₂ → 2FeO + 2SO₂ ↑

• Cu₂O + FeS → Cu₂S + FeO 

• 2Cu₂S + 3O₂ → 2Cu₂O + 2SO₂ ↑

• FeO + SiO₂ → FeSiO₃

Railway wagon axles are made by heating iron rods embedded in charcoal powder. This process is known as

• tempering

• case hardening

• sherardising

• annealing

Thomas slag is

• CaSiO₃

• Ca₃(PO₄)₂

• MnSiO₃

• CaCO₃

In the electrothermal process, the compound displaced by silica from calcium phosphate is

• calcium phosphide

• phosphine

• phosphorus

• phosphorus pentoxide

In froth floatation process for the purification of ores, the particles of ore float because

• their surface is not easily wetted by water

• they are light

• they are insoluble

• they bear electrostatic charge

Which of the following is not an ore of magnesium?

• Carnallite

• Dolomite

• Calamine

• Sea water