Calcium minerals are the raw materials for a variety of large-scale industrial processes. Which of the following is not an industrial process?

1. (a) Converting limestone, CaCO₃, to lime
2. (b) Converting fluorite, CaF₂, to HF
3. (c) Converting slaked lime, Ca(OH)₂, to lime
4. (d) Converting apatite minerals to phosphate fertilizers

Interpretation: To predict which option is not an industrial process among the given processes.

Concept introduction: Calcium is one of the most abundant elements found on earth. It is an alkaline earth metal and belongs to group 2A of the periodic table. Its compounds have a high melting point. Calcium occurs in various minerals that are found on earth’s surface. Some common minerals are limestone, dolomite, slaked lime, gypsum and chalk.

Calcium Oxide is quick lime and is a white, amorphous solid. Calcium hydroxide is known as slaked lime. Both are slightly soluble in water and dissolve in acids. Calcium carbonate is present in limestone and chalk. Calcium salts of fluoride and phosphates are also another important material. The formula for calcium fluoride is CaF2. The phosphates salt of calcium is known as apatites. Apatites have a general formula of Ca5X(PO4)3.

These calcium minerals are used as raw materials for the various large-scale industrial process to produce materials.

Reason for the correct options

The decomposition of limestone, CaCO3 to lime, CaO is one of the oldest methods. Limestone is easily available and is extracted from mines. It is then calcinated to produce lime. The chemical equation for this reaction is:

    CaCO3(s)→ΔCaO(s)+CO2(g)

The major use of calcium fluorite is in the manufacturing of hydrofluoric acid. The chemical reaction involved the reaction of calcium fluorite with concentrated sulfuric acid.

    CaF2(s)+H2SO4(l)→2HF(g)+CaSO4(s)

Apatites have a general formula of Ca5X(PO4)3