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CBSE · Class 10 · Science · Metals and Non-metalsExplain the extraction process of metals from their ores based on their position in the activity series. Specifically detail: Extraction of metals low in the reactivity series (with suitable chemical equations). Differentiate between Roasting and Calcination with chemical equations for metals in the middle of the reactivity series.

Step-by-Step Solution

Extraction of Metals Based on Reactivity

\nMetals are extracted from their ores based on their reactivity order in the activity series:


1. Extraction of Metals Low in the Reactivity Series\nMetals low in the reactivity series are very unreactive. The oxides of these metals can be reduced to metals by heating alone.

  • Example: Extraction of Mercury from Cinnabar ($HgS$):

    • Step 1: Cinnabar ($HgS$) is first heated in air to convert it into mercuric oxide ($HgO$). $$2HgS(s) + 3O_2(g) \xrightarrow{\Delta} 2HgO(s) + 2SO_2(g)$$
    • Step 2: Mercuric oxide is then reduced to mercury metal upon further heating. $$2HgO(s) \xrightarrow{\Delta} 2Hg(l) + O_2(g)$$
  • Example: Extraction of Copper from Copper Pyrites/Glance ($Cu_2S$): $$2Cu_2S(s) + 3O_2(g) \xrightarrow{\Delta} 2Cu_2O(s) + 2SO_2(g)$$ $$2Cu_2O(s) + Cu_2S(s) \xrightarrow{\Delta} 6Cu(s) + SO_2(g)$$


2. Difference Between Roasting and Calcination

\nMetals in the middle of the reactivity series (like $Fe, Zn, Pb$) are usually present as sulphides or carbonates in nature. Before reduction, they are converted into metal oxides using Roasting or Calcination.

FeatureRoasting (भर्जन)Calcination (निस्तापन)
DefinitionThe process of heating sulfide ores strongly in the presence of excess air.The process of heating carbonate ores strongly in limited air or absence of air.
Type of OreUsed for Sulphide ores.Used for Carbonate ores.
Gas EvolvedSulphur dioxide ($SO_2$) gas is liberated.Carbon dioxide ($CO_2$) gas is liberated.
Chemical Reaction ExampleZinc Sulphide ($ZnS$):<br>$2ZnS(s) + 3O_2(g) \xrightarrow{\Delta} 2ZnO(s) + 2SO_2(g)$Zinc Carbonate ($ZnCO_3$):<br>$ZnCO_3(s) \xrightarrow{\Delta} ZnO(s) + CO_2(g)$
\nAfter obtaining the metal oxide ($ZnO$), it is reduced to metallic zinc using a suitable reducing agent such as carbon (coke):
$$ZnO(s) + C(s) \rightarrow Zn(s) + CO(g)$$
💡 Study Guide: This question tests core syllabus concepts from Metals and Non-metals. For formulas, key summaries, and mock exam reference guides, read the full Metals and Non-metals Revision Notes.
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