Match each calcium-based compound or reagent listed on the left with its corresponding ind… — JAMB UTME

Match each calcium-based compound or reagent listed on the left with its corresponding industrial process, chemical behavior, or metallurgical function on the right.

Addition of calcium fluoride ( $\text{CaF}_2$ ) during the electrolytic extraction of calcium metalActs as a flux to lower the melting point of fused $\text{CaCl}_2$ from $800^\circ\text{C}$ to $600^\circ\text{C}$ and increase conductivity
Exothermic hydration of quicklime ( $\text{CaO}$ ) to yield slaked limeForms an alkaline suspension used in Clark's process to precipitate temporary hardness from water
Reaction of dry slaked lime ( $\text{Ca(OH)}_2$ ) with chlorine gas at room temperatureProduces bleaching powder ( $\text{CaOCl}_2 \cdot \text{H}_2\text{O}$ ) containing active hypochlorite ions
Rehydration and setting mechanism of Plaster of Paris ( $\text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O}$ )Crystallizes into monoclinic dihydrate gypsum ( $\text{CaSO}_4 \cdot 2\text{H}_2\text{O}$ ) accompanied by slight expansion

Answer

Calcium fluoride addition matches lowering the electrolyte melting point and enhancing conductivity; Calcium oxide hydration matches forming slaked lime used in water softening; Calcium hydroxide reaction with chlorine matches forming bleaching powder; Plaster of Paris rehydration matches forming dihydrate gypsum with volume expansion.

Each calcium compound or reagent is paired strictly according to its industrial function or chemical reaction behavior as specified in the JAMB UTME syllabus.

Step-by-Step Solution

Analyze the metallurgical role of calcium fluoride in calcium extraction

Identified

\text{CaF}_2

as a flux that lowers the melting point of fused

\text{CaCl}_2

from

800^\circ\text{C}

600^\circ\text{C}

Electrolysis of pure

\text{CaCl}_2

requires high temperature where molten calcium would dissolve in the electrolyte, so

\text{CaF}_2

is added as a flux.

Evaluate the chemical properties of calcium oxide and its slaked product

Slaking

\text{CaO}

gives

\text{Ca(OH)}_2

, which precipitates

\text{Ca(HCO}_3)_2

in Clark's method.

Calcium hydroxide reacts with hydrogen carbonate ions to precipitate insoluble

\text{CaCO}_3

, removing temporary hardness.

Determine the industrial reaction between slaked lime and chlorine

Chlorination of dry

\text{Ca(OH)}_2

yields bleaching powder,

\text{CaOCl}_2 \cdot \text{H}_2\text{O}

This specific gas-solid reaction forms active bleaching agents used in water treatment and industrial oxidation.

Examine the hydration chemistry of calcium sulfate hemihydrate

Plaster of Paris absorbs water to form gypsum with a slight increase in solid volume.

The crystallization process of gypsum yields interlocking monoclinic crystals that expand slightly to fill mold details perfectly.

Key Concept

Extraction, reactions, and industrial applications of alkaline earth metal (calcium) compounds.

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