The metallic aluminium is obtained from pure alumina in the presence of fused cryolite by

Pure bauxite is the best raw material for the manufacture of high alumina refractories, in which maximum alumina content can be as high as __________ percent.

A

55

B

70

C

80

D

90

Given that, 24 carat gold is pure gold, 18 carat gold is 3/4th of pure gold and 20 carat gold is 5/6th of pure gold, the ratio of the pure gold in 18 carat gold to the pure gold in 20 carat gold is -

A

5 : 8

B

10 : 9

C

8 : 5

D

9 : 10

Hot face insulating linings of high purity alumina fused mullite are used, where

A

Very high temperatures are involved

B

Highly reducing conditions are involved

C

Presence of iron or silica is harmful

D

All of the above

With increasing alumina content, the fusion point of high alumina refractories

A

Increases

B

Decreases

C

Remains constant

D

May increase or decrease ; depends on its alumina content

Maximum alumina content in high alumina refractory can be as high as __________ percent.

A

30

B

50

C

70

D

90

With increase in the alumina content, the refractoriness of high alumina refractories

A

Increases

B

Decreases

C

Remains same

D

May increase or decrease

Corundum and Cryolite are important ores of which of the following metals?

A

Silver

B

Iron

C

Aluminium

D

Tin

The metallurgical process in which a metal is obtained in a fused state is called

A

smelting

B

roasting

C

calcinations

D

froth floatation

Metallic soap (e.g. aluminium or calcium salts of fatty acids) can be used

A

As a lubricant

B

As a rust preventive

C

In hard water for cleaning of cloth

D

As a foam depressant in distillation column

Aluminium bronze contains aluminium and copper in the ratio of

A

50 : 50

B

40 : 60

C

60 : 40

D

10 : 90

The metallic aluminium is obtained from pure alumina in the presence of fused cryolite by

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