30 Questions
Which metal reacts the most vigorously with dilute hydrochloric acid?
Magnesium
What gas is liberated when metals react with dilute hydrochloric acid?
Hydrogen
Which metal forms nitrate salts when reacting with nitric acid?
Copper
What can dissolve noble metals like gold and platinum?
Aqua regia
Which metal is commonly used in Aqua Regia preparation?
Copper
What is formed when iron reacts with hydrochloric acid?
Iron chloride
What process is used to transform sulphide ores into oxides for easier metal extraction?
Roasting
Which of the following metals is NOT moderately reactive and thus used as a reducing agent for metal extraction?
Iron
In the reaction 3Mn + 2Al2O3 + heat -> 3 MnO2 + 4 Al, which substance undergoes oxidation?
Aluminium
What is the purpose of calcination in metal extraction?
To convert carbonates into oxides
Which metal is reduced by carbon in the extraction process discussed?
Zinc
Why are metals like sodium, calcium, and aluminium used as reducing agents in metal extraction?
They displace moderately reactive metals from their compounds
What is the main principle behind the hydraulic separation method described in the text?
Law of gravitation
In the Wilfley table method, why are the heavier particles collected on the slits between wooden riffles?
Because the gangue particles are heavier
What is the function of the forceful jet of water introduced in the hydraulic separation method tank?
To separate gangue particles from ore particles
What equipment is required for the Magnetic Separation Method mentioned in the text?
Electromagnetic machine
Why are gangue particles carried away with flowing water in the Wilfley table method?
Because they are lighter than ore particles
How does the hydraulic separation method differentiate particles?
By weight
What is the purpose of calcining the precipitate of Al(OH)3 obtained in Bayer's and Hall's processes?
To convert Al(OH)3 into alumina (Al2O3)
In the electrolytic reduction of alumina, what is the function of the graphite lining in the steel tank?
To act as the cathode
What role does cryolite (Na3AlF6) play in the extraction of aluminium?
It helps lower the melting point of the electrolyte
What happens to the anodes during the electrolysis of alumina?
They get oxidised
Why is molten aluminium collected at the bottom of the steel tank during electrolytic reduction?
Because it is heavier than the electrolyte
Which gas is liberated at the anode during the electrolysis of alumina?
Oxygen gas
What is the purpose of concentration of ores in metallurgy?
To separate gangue from ores
Which method is used for separating heavy particles of ores from light particles of gangue based on gravitation?
Wilfley table method
What is the function of the Wilfley table in the concentration of ores?
To separate heavy and light particles based on gravity
Why is the concentration of ores important in metallurgy processes?
To separate undesired components from ores
What determines the exact method to be used for concentrating ores in metallurgy?
All of the above
In the concentration of ores, why is separation based on gravitation effective?
It exploits differences in density
Study Notes
Reaction of Metals with Acids
- When metals (Al, Mg, Zn, Fe) react with dilute sulphuric acid or hydrogen chloride, salt and hydrogen gas are formed.
- The reactivity of these metals can be indicated by the following sequence: Mg > Al > Zn > Fe
- Examples of reactions:
- Mg(s) + 2HCl (aq) → MgCl2(aq) + H2(g)
- 2Al (s) + 6HCl (aq) → 2AlCl3(aq) + 3H2(g)
- Fe(s) + 2HCl (aq) → FeCl2(aq) + H2(g)
- Zn (s) + HCl (aq) → ZnCl2(aq) + H2(g)
Reaction of Metals with Nitric Acid
- Nitrate salts of metals are formed when metals react with nitric acid.
- Various oxides of nitrogen (N2O, NO, NO2) are also formed in accordance with the concentration of nitric acid.
- Examples of reactions:
- Cu(s) + 4 HNO3 (aq) (Concentrated) → Cu(NO3)2(aq) + 2NO2(g) + 2H2O (l)
- Cu(s) + 8HNO3 (aq) (Dilute) → Cu(NO3)2(aq) + 2NO(g) + 4H2O (l)
Reaction of Metals with Salts of Other Metals
- Metals can be extracted in pure form and then purified by different methods of purification.
- This entire process is called metallurgy.
Basic Principles of Metallurgy
- Pure metal is obtained from the ore by the following stages:
- Concentration of ores
- Separation of gangue from the ore
- Purification of the metal
- Various ways are used for concentration of ores, depending on the physical properties of the metal and the gangue.
- Examples of methods for concentration of ores:
- Separation based on gravitation
- Magnetic separation
- Hydraulic separation method
Extraction of Aluminium
- Alumina is extracted from the ore by the following steps:
- Concentration of ores
- Separation of gangue from the ore
- Purification of alumina
- Alumina is then reduced to aluminium by electrolysis.
- The electrolysis is done in a steel tank with a graphite lining.
- The electrode reactions are:
- Anode reaction: 2O2 → O2 + 4e-
- Cathode reaction: Al3+ + 3e- → Al
Extraction of Moderately Reactive Metals
- Moderately reactive metals such as iron, zinc, lead, and copper occur in nature as sulphide salts or carbonates.
- These metals are obtained by roasting or calcination of their ores.
- Roasting: 2ZnS + 3O2 → 2ZnO + 2SO2
- Calcination: ZnCO3 → ZnO + CO2
- The metal oxide is then reduced to the metal by using a suitable reductant such as carbon.
- Example: ZnO + C → Zn + CO
Test your knowledge on mineral processing methods such as the Wilfley table method and hydraulic separation method. Learn about how lighter gangue particles are separated from heavier mineral particles using these techniques.
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