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Question
What do you observe when caustic soda solution is added to the following solution, first a little and then in excess:
ZnSO4
Write a balanced equation for this reaction.
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Solution
\[\ce{\underset{\text{Colourless}}{ZnSO4} + 2NaOH -> \underset{\text{white gelatinous ppt.}}{Zn(OH)2↓} + \underset{\text{Colourless}}{Na2SO4}}\]
In excess of alkali , White gelatinous ppt. of Zn(OH)2 becomes soluble :
\[\ce{Zn(OH)2 + 2NaOH(excess) -> \underset{\text{Sodium Zincate (Colourless)}}{Na2ZnO2 + 2H2O}}\]
RELATED QUESTIONS
Name a white, insoluble oxide that dissolves when fused with caustic soda or caustic potash.
Using sodium hydroxide solution, how will you distinguish: Zinc nitrate solution from calcium nitrate solution
Using Sodium hydroxide solution, how would you distinguish: Iron(II) chloride from Iron (III) chloride
Sodium hydroxide solution is added first in a small quantity, then in excess to the aqueous salt solutions of copper (II) sulphate, zinc nitrate, lead nitrate, calcium chloride, and iron (III) sulphate. Copy the following table and write the colour of the precipitate in (i) to (v) and the nature of the precipitate (soluble or insoluble) in (vi) to (x).
| Aqueous salt solution | Colour of precipitate when NaOH is added in a small quantity | Nature of precipitate (soluble or insoluble) when NaOH is added in excess |
| Copper (II) sulphate | (i) | (vi) |
| Zinc nitrate | (ii) | (vii) |
| Lead nitrate | (iii) | (viii) |
| Calcium chloride | (iv) | (ix) |
| Iron (III) Sulphate | (v) | (x) |
Sodium hydroxide solution is added to the solutions containing the ions mentioned in List X. List Y gives the details of the precipitate. Match the ions with their coloured precipitates.
| List X | List Y |
| (i) Pb2+ | (A) Reddish Brown |
| (ii) Fe2+ | (B) White insoluble inexcess |
| (iii) Zn2+ | (C) Dirty green |
| (iv) Fe3+ | (D) White soluble in excess |
| (v) Cu2+ | (E) White soluble in excess |
| (vi) Ca2+ | (F) Blue |
Distinguish by adding:
Sodium hydroxide solution and ammonium hydroxide solution to calcium salt solution and lead salt solution.
Distinguish by adding:
Sodium hydroxide solution and ammonium hydroxide solution to lead nitrate solution and zinc nitrate solution.
What is observed when hot, concentrated caustic soda solution is added to zinc? Write a balanced equation.
What is observed when hot, concentrated caustic soda solution is added to aluminium? Write a balanced equation.
Identify the cation in the following case:
Sodium hydroxide solution when added to Solution C gives a white precipitate which is insoluble in excess of sodium hydroxide solution.
