Tag: extraction of metals by electrolysis

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Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

(a) Roasting and calcination are the two processes to reduce the metal oxides to the respective metals.
(b) Magnesium is extracted from its ore by electrolytic reduction process.
(c) Cryolite is used in metallurgy of aluminium in order to increase the fusibility and conductivity
(d) I Hall's process bauxite is leached with the help of ${Na} _{2}{CO} _{3}$.
Which of the following options regarding the above statements is correct?

  1. a, b and c

  2. b, c and d

  3. c and d

  4. only a
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

(b) Magnesium is extracted from its ore by electrolytic reduction process.
(c) Cryolite is used in metallurgy of aluminium in order to increase the fusibility and conductivity
(d) I Hall's process bauxite is leached with the help of ${Na} _{2}{CO} _{3}$. statements are correct. The concentrated ore is converted into metal oxide by calcination or roasting.

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

State the function of fluorspar in the metallurgy of aluminium.

  1. to increase conductivity

  2. to decrease conductivity

  3. to increase ductility

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Pure alumina melts at about $2000^oC$ and is a bad conductor of electricity. If fused cryolite and fluorspar is added, the mixture melts at $900^0C$ and solution becomes a good conductor of electricity. 

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

State the function of cryolite?

  1. to increase conductivity

  2. to decrease conductivity

  3. to increase ductility

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Pure alumina melts at about $2000^oC$ and is a bad conductor of electricity. If fused cryolite and fluorspar is added, the mixture melts at $900^oC$ and solution becomes a good conductor of electricity. 

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

The electrolyte used in electrolytic refining of impure aluminium is __________.

  1. $AI _2O _{3} + CaF _{2}$
  2. $Na _{3}AlF _{6} + CaF _{2}$
  3. $Al _2O _{3}, Na _{3}AlF _{6} and CaF _{2}$

  4. Any aluminium salt is molten state
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In the metallurgy of aluminium, purified $Al _2O _3$ is mixed with $Na _3AlF _6$ or $CaF _2$ which lowers the melting point of the mix and brings conductivity.

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

In the electrolytic reduction of alumina, the electrolyte is covered with coke powder because, it __________.

  1. prevents oxidation of aluminium formed

  2. reacts with aluminium forming aluminium carbide

  3. prevents heat loss from the electrolyte

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The electrolytic mixture is sprinkled with coke to prevent the anode's oxidation by the oxygen evolved

Also, more material to the top of the anode is continuously added in the form of briquettes made from coke and pitch. The lost heat from the smelting operation is used to bake the briquettes into the carbon form required for reaction with alumina.
Therefore, $C$ is correct

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

Aluminum is used for making cooking utensils. which of the following propertis of aluminium are responsible for the same ?
(i) Good thermal conductivity ctrical conductivity
(ii) Good electrical conductivity
(iii) Ductillity
(iv) High melting point

  1. (i) and (ii)

  2. (i) and (iii)

  3. (ii) and (iii)

  4. (i) and (iv)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Aluminium is used for making cooking utensils,the properties used.

(1)Good thermal conductivity & electrical conductivity.
Thermal conductivity good implies laser cooking and saves time.
(ii)Malleable property chelps it to easily shape into utensils.
(iii)High melting point would ensure utensils don't melt on cooking temperature.

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

The mass of carbon anode consumed (giving of carbon dioxide) in the production of $270 \ kg$ aluminium metal bum bauxite by Hall process is: (Atomic mass $Al = 27$)

  1. $180$ kg
  2. $270$ kg
  3. $540$ kg
  4. $90$ kg
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The chemical reaction for the Hall process is given by

$2Al _2O _3+3C\rightarrow 4Al+3CO _2$
Moles of aluminium produced$=\dfrac{270000}{27}=10000$
According to the reaction,
$10000 \; kg$ moles of aluminium can be produced by consuming $2500\times3=7500 \ moles $ of Carbon
Hence mass of carbon=$12\times 7500=90000\ g=90\ kg$

Therefore, D is the correct answer

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

In case of Hall's process applied on reduction of $Al _2O _3$ to Al can be done by using:

  1. Cathode - Al, Anode - Graphite

  2. Cathode - Graphite, Anode - Graphite

  3. Cathode - Graphite, Anode - Steel

  4. Cathode - Steel, Anode - Graphite
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Both are graphite 

since in Hall's Process both the terminals are carbon content.