The substance not likely to contain {CaCO}₃ is

Correct Answer is : calcined gypsum

Correct Answer is : calcined gypsum

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CGPET 2013 Solved Paper

Section: Chemistry

Question : 58 of 150

Marks: +1, -0

\mathrm{CaCO}_3

Solution:

Gypsum is a very soft sulphate mineral composed of calcium sulphate dihydrate, with the chemical formula

\mathrm{CaSO}_4 \cdot 2 \mathrm{H}_2\mathrm{O}

On heating, gypsum loses water and gives the hemihydrate

\left(\mathrm{CaSO}_4 \cdot \frac{1}{2} \mathrm{H}_2\mathrm{O}\right)

or the anhydrite.

\underset{\text{gypsum}}{2\mathrm{CaSO}_4 \cdot 2 \mathrm{H}_2\mathrm{O}} \xrightarrow{120^{\circ}\mathrm{C}}

\underset{\text{plaster of Paris (Calcium sulphate hemihydrate)}}{(\mathrm{CuSO}_4)_2 \cdot \mathrm{H}_2\mathrm{O} + 3 \mathrm{H}_2\mathrm{O}}

The hemihydrate is known as calcined gypsum or plaster of Paris.

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