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Difficulty: MediumAlkaline Earth Metals: Calcium Extraction, Properties, and Compounds

Match each calcium compound or reagent listed on the left with its corresponding industrial preparation, chemical property, or role on the right.

  • Quicklime (CaO\text{CaO})Obtained by the thermal decomposition of limestone (CaCO3\text{CaCO}_3) at high temperatures.
  • Slaked lime (Ca(OH)2\text{Ca(OH)}_2)Formed by adding a controlled amount of water to quicklime; used in lime water tests for carbon dioxide.
  • Plaster of Paris (CaSO4⋅12H2O\text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O})Obtained by partially dehydrating gypsum (CaSO4⋅2H2O\text{CaSO}_4 \cdot 2\text{H}_2\text{O}) by heating around 120∘C120^\circ\text{C}.
  • Calcium fluoride (CaF2\text{CaF}_2)Added as a flux to lower the melting point of fused CaCl2\text{CaCl}_2 during the electrolytic extraction of calcium.

Answer

Quicklime (CaO\text{CaO}) matches with thermal decomposition of limestone; Slaked lime (Ca(OH)2\text{Ca(OH)}_2) matches with adding water to quicklime; Plaster of Paris (CaSO4⋅12H2O\text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O}) matches with partial dehydration of gypsum; Calcium fluoride (CaF2\text{CaF}_2) matches with electrolyte flux in calcium extraction.
Each calcium compound is accurately paired with its definitive reaction or industrial application in standard JAMB UTME chemistry syllabus specifications.

Step-by-Step Solution

1
Identify the industrial reaction for Quicklime (CaO\text{CaO}).
Quicklime is formed via CaCO3(s)→CaO(s)+CO2(g)\text{CaCO}_3(\text{s}) \rightarrow \text{CaO}(\text{s}) + \text{CO}_2(\text{g}).
Thermal decomposition of limestone yields calcium oxide.
2
Identify the process of slaking lime to form Slaked lime (Ca(OH)2\text{Ca(OH)}_2).
Slaking quicklime CaO(s)+H2O(l)→Ca(OH)2(s)\text{CaO}(\text{s}) + \text{H}_2\text{O}(\text{l}) \rightarrow \text{Ca(OH)}_2(\text{s}) produces calcium hydroxide.
Calcium hydroxide solution (limewater) is used to detect CO2\text{CO}_2 gas.
3
Determine the formula and production method of Plaster of Paris.
Heating gypsum (CaSO4⋅2H2O\text{CaSO}_4 \cdot 2\text{H}_2\text{O}) yields hemihydrate CaSO4⋅12H2O\text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O}.
Controlled dehydration removes 1.51.5 molecules of crystallization water per mole of calcium sulfate.
4
Determine the function of Calcium fluoride (CaF2\text{CaF}_2) in metallurgy.
Acts as a flux in fused CaCl2\text{CaCl}_2 electrolysis.
It lowers the melting point of anhydrous CaCl2\text{CaCl}_2 from about 772∘C772^\circ\text{C} to around 650∘C650^\circ\text{C}.

Key Concept

Chemical transformations, properties, and metallurgical roles of calcium and its principal compounds.
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Topics

Alkaline Earth Metals: Calcium Extraction, Properties, and Compounds

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