Engineering Questions with Answers - Multiple Choice Questions

Chemical Industry MCQ’s – Aluminum

1 - Question

Which among the following is a major source of aluminium oxide?
a) Hematite
b) Siderite
c) Magnetite
d) Bauxite
View Answer Answer: d
Explanation: The major source of aluminium oxide used in electrolytic reduction cells is bauxite. Bauxite consists of 50-60% of alumina, silica and ore. Hematite, siderite and magnetite are ores of iron.

2 - Question

What is the pressure maintained in the autoclave while manufacturing steel?
a) 1atm
b) 2atm
c) 0.5atm
d) 4.5atm
View Answer Answer: d
Explanation: Bauxite ore if fed to jaw crusher. Then the ore is mixed with concentrated caustic in an autoclave digester at 4.5atms. High pressure is maintained for 100% conversion to sodium aluminate.

3 - Question

How is crystallization of trihydrate induced while manufacturing aluminium?
a) Mixing
b) Cooling
c) Heating
d) Agitation
View Answer Answer: b
Explanation: The slurry is washed in a series of counter current thickeners. The sodium aluminate is clarified via a rotary filter. The diluted mixture is cooled and seeded in a precipitator to induce crystallization of trihydrate.

4 - Question

Recovery of alumina from red mud is the most difficult process during the manufacture of aluminium.
a) True
b) False
View Answer Answer: a
Explanation: Recovery of alumina from red mud discharged from the thickener is the major engineering problem in the manufacture of aluminium. Alternative method is to calcine the mud with lime and soda ash to form sodium aluminate which can be leached.

5 - Question

How is alumina converted to aluminium?
a) Heating
b) Cooling
c) Electrolytically using an aluminium smelting cell
d) Adding coke
View Answer Answer: c
Explanation: Alumina is periodically reduced to aluminium by electrolysis. A molten cryolite bath is maintained at 1000°C. Reduction takes place at the graphite anodes.

6 - Question

How is carbon electrodes formed in an electrolytic aluminium smelting cell?
a) From Alumina
b) By Replacing the old electrodes
c) From coke and carbon dioxide
d) From coke and pitch
View Answer Answer: d
Explanation: Carbon electrodes are formed continuously from coke and pitch. Pitch is a soft to hard and brittle coal substance.

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