Zinc sulphate heptahydrate is commonly known as white vitriol. It is obtained by dissolving zinc, zinc oxide, zinc hydroxide, zinc carbonated in dilute H2SO4. The solution of zinc sulphate on crystallization gives colorless crystal of ZnSO4 7H2O.
Zn + H2SO4 → ZnSO4 + H2O
Zn + H2SO4 → ZnSO4 + H2O
Zn (OH)2 + H2SO4 → ZnSO4 + 2H2O
Zn CO3 + H2SO4 → ZnSO4 + H2O + CO2
ZnSO4 (aq) crystallization → ZnSO4 7H2O
White Vitriol
In large, ZnSO4 is obtained by heating ZnS in air below 9000c
ZnS + O2 below 900 → ZnSO4
** Properties:**
(Crystalline) ZnSO4 7H2O is colorless crystalline solid white anhydrous ZnSO4 7H2O is an efflorescent solid.
ZnSO4 7H2O is an efflorescent solid and effloresces when exposed in air to give monohydrate. The last H2O molecule is lost at 3000c.
ZnSO4 7H2O exposed in air → ZnSO4 H2O + 6H2O
ZnSO4 H2O 300 → 2Zn + SO2 + H2O
The anhydrous zinc Sulphate on heating above 9000c decomposes forming ZnO.
2ZnSO4 (aq) above 900 → 2ZnO + SO2 + O2
Action of NaOH:-
ZnSO4 solution gives off-white ppt of Zn (OH)2 with NaOH which dissolves on adding excess NaOH forming sod. Zincate.
ZnSO4 + 2NaOH → Zn(OH)2 + Na2SO4
Zn(OH)2 + 2NaOH → Na2ZnO2 + 2H2O
** Uses:**
- It is used in medicine
- It is used as mordant in dying.
- It is used as electrolyte in electroplating of zinc.
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