Metal Extraction Processes

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Questions and Answers

Which of the following statements accurately describes the extraction of metals low in the activity series?

  • The oxides of these metals require strong reducing agents like carbon for their reduction due to the high stability of their oxides.
  • The direct heating of sulphide ores effectively yields pure metals, bypassing the oxide formation step due to the exothermic nature of the reaction.
  • The oxides of these metals can be directly reduced to metals by heating alone, owing to the low reactivity of the metals. (correct)
  • These metals are typically extracted through electrolysis of their molten chlorides because of their strong affinity for oxygen.

Why is it generally necessary to convert metal sulphides and carbonates into oxides before reduction when extracting metals in the middle of the activity series?

  • It is easier to obtain a metal from its oxide, as compared to its sulphides and carbonates. (correct)
  • The direct reduction of sulphides and carbonates is thermodynamically more favorable, yielding a higher purity metal product.
  • Sulphides and carbonates react violently with common reducing agents, posing safety hazards that oxides do not.
  • Sulphides and carbonates are more readily available in nature compared to oxides, making them the preferred starting materials for metal extraction.

In the extraction of zinc from zinc blende ($ZnS$), which of the following sequences of steps is typically employed?

  • Electrolytic reduction of the molten ore.
  • Roasting followed by reduction with carbon. (correct)
  • Direct reduction with a more reactive metal like sodium.
  • Calcination followed by reduction with carbon.

During the roasting of sulphide ores, what is the primary environmental concern associated with the process?

<p>The evolution of sulfur dioxide ($SO_2$), which can cause acid rain. (A)</p> Signup and view all the answers

Which of the following methods is most suitable for extracting metals that lie in the middle of the activity series, such as iron and zinc?

<p>Reduction of their oxides with carbon. (C)</p> Signup and view all the answers

In the calcination process, what is the main purpose of heating carbonate ores in limited air?

<p>To convert the carbonate to its corresponding oxide. (D)</p> Signup and view all the answers

What is the role of highly reactive metals like sodium, calcium, and aluminum in the extraction of certain metals from their oxides?

<p>They serve as reducing agents, displacing the desired metal from its oxide. (D)</p> Signup and view all the answers

Consider a scenario where a metal oxide, $M_2O_3$, is reduced using carbon. Which of the following correctly represents a balanced chemical equation for this process?

<p>$2M_2O_3(s) + 3C(s) \xrightarrow{Heat} 4M(s) + 3CO(g)$ (B)</p> Signup and view all the answers

Flashcards

Metals low in the activity series

Unreactive metals that can be extracted by heating their oxides.

Cinnabar

Mercury sulfide (HgS); an ore of mercury.

Roasting

Heating a sulphide ore in excess air to convert it to an oxide.

Calcination

Heating a carbonate ore in limited air to convert it to an oxide.

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Metals in the middle of activity series

Metals with moderate reactivity, often found as sulphides or carbonates.

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Reduction (in metal extraction)

A process where a metal is obtained from its compound.

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Displacement reactions

Using a more reactive metal to displace a less reactive metal from its oxide.

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Reducing agents

Substances such as carbon, sodium, calcium or aluminum that remove oxygen from metal oxides.

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