Chemistry XII Content
Copper Sulphate pentahydrate (CuSO4 5H2O) is commonly known as Blue Vitriol. It is obtained in lab by dissolving CuO, Cu(OH)2 or CuCO3 in dil H2SO4. The solution on crystallization gives blue triclinic crystals of CuSO4 5H2O.
CuO + H2SO4 → CuSO4 + H2O
Cu(OH)2 + H2SO4 → CuSO4 + H2O
CuCO3 + H2SO4 → CuSO4 + H2O + CO2
CuSO4 crystallization → CuSO4 5H2O
In large scale, CuSO4 is obtained by reacting scrap copper with hot and dilute H2SO4 in presence of wir.
2Cu + 2H2SO4 + O2 → 2CuSO4 + H2O
Hot & dil
i. Hydrated copper sulphate is blue crystalline solid while anhydrous CuSO4 is white amorphous solid.
ii. It is soluble in water.
iii. Action of heat:
Blue vitriol on heating losses 4 molecules of water at 1000c to give monohydrate form and at 2300c to give anhydrous CuSO4.
CuSO4 5H2O 100 → CuSO4H2O 230 → CuSO4
Blue blueish white white
Anhydrous CuSO4 gives back blue vitrial in contact with water so anhydrous CuSO4 is used to detect water.
Anhydrous CuSO4 on further heating decompose forming CuO.
CuSO4 above 230 → CuO + SO3
iv. Action of water:
CuSO4 gives acidiec salt solution due to hydrolysis of Cu++ ion as it. Is salt of weak base and strong acid.
CuSO4 (aq) → Cu++ + SO4
Cu++ + 2H2O → Cu (OH)2 + 2H+
v. Reaction with KI:
KI reduces CuSO4 to cuprous iodide which appears as white ppt while KI is oxidized to I2
vi. Reaction with NH3:
when NH3 is added to CuSO4 solution, a bluish white ppt of Cu(OH)2 is formed which dissolves in excess ammonia forming tetra amine copper (II) sulphate which is commonly known as Schweizer’s reagent.
CuSO4 + NH4OH → Cu(OH3)4SO4
CuSO4 + NH4OH + (NH4)2SO4 → [Cu(NH3)4]SO4 + 4H2O
Tetra amine copper (ii) sulphate (deep blue)
- It is used as electrolyte in purification of copper & electroplating of Cu.
- It is used in making schweizer’s reagent used for mfg of paper.
- It is used as pesticide in controlling aphids and fungal growth.