Refining plays an essential role in metal extraction from its ore. Metal is typically extracted in its impure form from its ore. This impure metal is known as crude metal. We use refining to remove the impurities and extract the metal in its high purity. We can remove contaminants from crude metal in numerous ways established on the metal and impurity properties. Distillation, electrolysis, liquation, vapour phase refining, and zone refining are some techniques used to remove impurities from a crude metal.
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Definition: Refining is a process of removing impurities to obtain a metal of high purity. |
Refining Chemistry Questions with Solutions
Q1. Which of the following impurity is not present in the crude metals?
(a) Other metals
(b) Pine oil
(c ) Unreacted oxides
(d) None of the above
Answer: (b) Pine oil is not present in crude metals. Non-metals like silicon, phosphorus, and unreacted oxides of the metals are present in the crude metals.
Q2. Which of the following metals cannot be refined by distillation?
(a) Tin
(b) Zinc
(c ) Mercury
(d) None of the above
Answer: (a) Tin cannot be refined by distillation.
Q3. Zone refining is also known as fractional crystallisation.
(a) True
(b) False
(c ) Neither true nor false
(d) None of the above
Answer: (a) True. Zone refining is also known as fractional crystallisation.
Q4. Which of the following electrolyte is used during the electrolytic refining of copper?
(a) Copper sulphate solution acidified with sulphuric acid
(b) Copper sulphate solution
(c ) Sulphuric Acid
(d) None of the above
Answer: Copper sulphate solution acidified with sulphuric acid is used during the electrolytic refining of copper.
Q5. Which of the following can not be refined by the zone refining?
(a) Germanium
(b) Silicon
(c ) Gold
(d) None of the above
Answer: (c ) Gold can not be refined by the zone refining.
Q6. Why is zone refining carried out in an inert atmosphere?
(a) To prevent oxidation of metal
(b) To prevent reduction of metal
(c ) To reduce the external temperature
(d) To reduce the superficial pressure
Answer: (a) Zone refining carried out in an inert atmosphere to prevent oxidation of the metal.
Q7. What is refining?
Answer: Refining is a process of removing impurities to obtain a metal of high purity. We can remove it from the crude metal in numerous ways established on the metal and impurity properties. We can use the following techniques to purify crude metals.
1. Distillation
2. Electrolysis
3. Vapour phase refining
4. Liquation
5. Zone refining
6. Chromatographic methods
Q8. Why do we convert a sulphide ore to oxide before reduction?
Answer: We convert a sulphide ore to oxide before reduction because sulphide does not reduce while oxides reduce readily.
Q9. What is flux? Explain its necessity in the refining process.
Answer: Flux is a substance added to the smelting of ores to facilitate fluidity and vacate impurities in the form of slag.
The primary function of flux is to remove gangue. Moreover, it also makes the molten mass more conducting.
Q10. What is the chemical formula of bauxite?
Answer: The chemical formula of bauxite is Al2O3. 2 H2O. It is an essential ore of aluminium.
Q11. What is calcination?
Answer: Calcination is the process in which ore is heated without air or a limited quantity of air or oxygen.
CaCO3 → CaO + CO2
Q12. What is roasting?
Answer: Roasting is the process of heating a sulfide ore to a high temperature below its melting point in the presence of air or oxygen.
2 ZnS + 3 O2 → 2 ZnO + 2 SO2
Q13. Match the following.
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Column A |
Column B |
|---|---|
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R2C = CR2 → R2CHCHR2 |
Roasting |
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ZnCO3 → ZnO + CO2 |
Calcination |
|
2 ZnS + 3 O2 → 2 ZnO + 2 SO2 |
Thermite process |
|
Fe2O3 + 2 AI → 2 Fe + AI2O3 |
Addition reaction |
Answer:
|
Column A |
Column B |
|---|---|
|
R2C = CR2 → R2CHCHR2 |
Addition reaction |
|
ZnCO3 → ZnO + CO2 |
Calcination |
|
2 ZnS + 3 O2 → 2 ZnO + 2 SO2 |
Roasting |
|
Fe2O3 + 2 AI → 2 Fe + AI2O3 |
Thermite process |
Q14. What are the primary steps of metal extraction from its ore?
Answer: The primary step of extracting metal from its ore is mentioned below.
1. Crushing of the ore
2. The concentration of the ore
3. Reduction or isolation of the crude metal from its ore
4. Purification or refining of the metal
Q15. How will you differentiate between calcination and roasting?
Answer: We can distinguish between calcination and roasting in the following ways.
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S. No. |
Calcination |
Roasting |
|---|---|---|
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1. |
Calcination is a process in which ore is heated without air or a limited quantity of air. |
Roasting involves heating ore below its melting point in the presence of air or oxygen. |
|
2. |
Calcination involves the thermal decomposition of carbonate ores. |
Roasting is carried out mostly for sulfide minerals. |
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3. |
During calcination, moisture is driven out from an ore. |
Roasting does not involve dehydration of ore. |
|
4. |
CaCO3 → CaO + CO2 |
2 ZnS + 3 O2 → 2 ZnO + 2 SO2 |
|
5. |
Carbon dioxide is given out during calcination. |
During roasting, many toxic metallic and acidic compounds are released. |
Practise Questions on Refining
Q1. How is copper extracted from low-grade copper ore?
Q2. What are the two fundamental necessities of refining metal by the Mond and Van Arkel process?
Q3. What are the two fundamental necessities of refining metal by vapour phase refining?
Q4. Which of the following method can be used to prepare copper of high purity?
Q5. Which of the following process is not used for the purification of Bauxite?
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