Extraction of Metals Low Medium High Reactivity - UNSOLVED PRACTICE SET

Q7. Name the three methods of extraction of metals based on their reactivity. Give one example of a metal extracted by each method.

Q8. Differentiate between roasting and calcination with one example of each.

Q9. Your father explains that iron is made in a large furnace called a blast furnace. He says coke (carbon), limestone, and iron ore are added from the top. Explain the role of each material in the extraction of iron.

Q10. Why is aluminium extracted by electrolysis and not by reduction with carbon? Explain.

Q11. Write the chemical equations for the extraction of zinc from zinc blende (ZnS), showing the steps of roasting and reduction.

Q12. What is the thermite reaction? Write the chemical equation and mention one application of this reaction.

Q13. Describe the extraction of metals based on their reactivity. Explain how metals of low reactivity (like mercury), medium reactivity (like iron and zinc), and high reactivity (like aluminium and sodium) are extracted from their ores. Write chemical equations for the extraction of iron in the blast furnace and aluminium by electrolysis.

Q14. A student visits an iron and steel plant and observes the following:

Raw materials: Iron ore (haematite), coke, limestone, and hot air

The furnace is very tall and hot at the bottom

Molten iron collects at the bottom

Slag floats on top of the molten iron

(a) Write the chemical equation for the reduction of iron oxide by carbon monoxide.

(b) Explain the role of limestone in the blast furnace. Write the chemical equation for the formation of slag.

(c) Why is hot air blasted from the bottom of the furnace?

(d) Why does molten iron collect at the bottom while slag floats on top?

(e) What is the difference between pig iron and cast iron?

Q15. "The method of extraction of a metal from its ore is determined by its position in the reactivity series, and this has shaped human civilization from the Bronze Age to the Space Age." Discuss this statement by explaining: (i) how the discovery of copper and iron extraction led to the Bronze Age and Iron Age, (ii) why aluminium became widely used only after the invention of electrolysis, (iii) the environmental impact of different extraction methods, and (iv) how modern extraction techniques are becoming more sustainable.

Q16. A steel plant in India processes iron ore to produce steel:

(a) The plant uses haematite (Fe₂O₃) as the iron ore. If 1600 tonnes of Fe₂O₃ are processed daily, calculate the theoretical mass of iron produced. (Molar masses: Fe₂O₃ = 160 g/mol, Fe = 56 g/mol)

(b) The actual yield is 85% of the theoretical yield. Calculate the actual mass of iron produced.

(c) The reaction in the blast furnace is: Fe₂O₃ + 3CO → 2Fe + 3CO₂. Calculate the mass of CO required to reduce 1600 tonnes of Fe₂O₃. (Molar mass of CO = 28 g/mol)

(d) If coke is 90% carbon, calculate the mass of coke needed to produce the required CO. (C + ½O₂ → CO)

(e) The slag formed is CaSiO₃. If limestone (CaCO₃) provides the CaO, calculate the mass of limestone needed. (Molar masses: CaCO₃ = 100 g/mol, CaO = 56 g/mol)

Q17. An aluminium extraction plant uses the Hall-Heroult process:

(a) Write the chemical equation for the electrolysis of molten aluminium oxide (Al₂O₃).

(b) If the plant produces 270 kg of aluminium daily, calculate the mass of Al₂O₃ required. (Molar masses: Al₂O₃ = 102 g/mol, Al = 27 g/mol)

(c) Calculate the mass of oxygen released as a by-product.

(d) The process requires cryolite (Na₃AlF₆) to lower the melting point of Al₂O₃. Why is this necessary?

(e) If electricity costs ₹6 per kWh and the process requires 15 kWh per kg of aluminium, calculate the daily electricity cost. Why is aluminium called "congealed electricity"?

Q18. A copper extraction plant in India processes copper pyrites (CuFeS₂):

(a) The ore is first roasted: 2CuFeS₂ + O₂ → Cu₂S + 2FeS + SO₂. If 368 kg of CuFeS₂ is roasted, calculate the mass of Cu₂S formed. (Molar masses: CuFeS₂ = 184 g/mol, Cu₂S = 159 g/mol)

(b) The Cu₂S is then heated in air to form blister copper: Cu₂S + O₂ → 2Cu + SO₂. Calculate the mass of copper obtained from the Cu₂S in part (a). (Atomic mass of Cu = 63.5)

(c) The Khetri copper mines in Rajasthan are famous for copper extraction. Why is copper considered a metal of medium reactivity?

(d) If the plant produces 100 tonnes of blister copper daily, and the ore contains 2% CuFeS₂, calculate the mass of ore processed daily.

(e) The SO₂ produced is a pollutant. How can it be utilized to prevent environmental damage?