State what happens when:(i) Gypsum is heated at 373K.(ii) Blue crystals of CuSO4 are heated.(iii) Excess of CO2 gas is passed through lime water.

i> The chemical name of Gypsum is Calcium Sulphate Dihydrate.

The chemical formula of gypsum is CaSO4.2H2O   When gypsum is heated at 373K, It will form plaster of pairs and water.

$CaSO_{4} .2H_{2} O\xrightarrow{heat} CaSO_{4} .\frac{1}{2} H_{2} O+1\frac{1}{2} H_{2} O$

Gypsum → Plaster of Paris + Water

ii> One formula unit of hydrated copper sulphate contains five water molecules (5H20). The water molecules which form part of the structure of a crystal are called water of crystallization.
When heated it loses its blue colour and crystal shape to become a powdery white mass.
$CuSO_{4} .5H_{2} O\ \xrightarrow{heat} CuSO_{4} \ +\ 5H_{2} O$
Blue                              White
iii> Carbon dioxide reacts with limewater (a solution of calcium hydroxide, Ca(OH)2), to form a white precipitate (appears milky) of calcium carbonate, CaCO3.
$Ca( OH)_{2}( aq) \ +\ CO_{2}( g) \ \rightarrow \ CaCO_{3}( s) \ +\ H_{2} O( l)$
On adding more carbon dioxide, it results in the precipitate dissolving to form a colourless solution of calcium hydrogen carbonate.
$CaCO_{3}( s) \ +\ CO_{2}( g) \ +\ H_{2} O( l) \ \rightarrow \ Ca( HCO_{3})_{2}( aq)$


Simply Easy Learning

Updated on: 10-Oct-2022


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