This set of Chemical Industry Multiple Choice Questions & Answers (MCQs) focuses on “Aluminum”.
1. Which among the following is a major source of aluminium oxide?
a) Hematite
b) Siderite
c) Magnetite
d) Bauxite
View Answer
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. What is the pressure maintained in the autoclave while manufacturing steel?
a) 1atm
b) 2atm
c) 0.5atm
d) 4.5atm
View Answer
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. How is crystallization of trihydrate induced while manufacturing aluminium?
a) Mixing
b) Cooling
c) Heating
d) Agitation
View Answer
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. Recovery of alumina from red mud is the most difficult process during the manufacture of aluminium.
a) True
b) False
View Answer
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. How is alumina converted to aluminium?
a) Heating
b) Cooling
c) Electrolytically using an aluminium smelting cell
d) Adding coke
View Answer
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. 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
Explanation: Carbon electrodes are formed continuously from coke and pitch. Pitch is a soft to hard and brittle coal substance.
Sanfoundry Global Education & Learning Series – Chemical Industry.
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