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Solutions for Chemistry, Class 10, ICSE
Sodium hydroxide solution is added first in a small amount, then in excess to the aqueous salt solutions of:
State in each case :
(i) the colour of the precipitate when NaOH is added in a small quantity;
(ii) the nature of the precipitate [i.e. soluble or insoluble] when NaOH is added in excess.
Answer
(i) The colour of the precipitate when NaOH is added in a small quantity are as follows —
(ii) the nature of the precipitate [i.e. soluble or insoluble] when NaOH is added in excess are as follows —
Write balanced equations for — (a) Aluminium (b) Zinc — is warmed with NaOH [caustic soda] soln.
Answer
Aluminium
2Al + 2NaOH + 2H2O ⟶ 2NaAlO2 + 3H2
Zinc
Zn + 2NaOH ⟶ Na2ZnO2 + H2
The questions below refers to the following salt solutions listed A to F:
A: Copper nitrate
B: Iron [II] sulphate
C: Iron [III] chloride
D: Lead nitrate
E: Magnesium sulphate
F: Zinc chloride
(i) Which soln. becomes a deep/inky blue colour when excess of ammonium hydroxide is added to it.
(ii) Which solution gives a white precipitate with excess ammonium hydroxide solution.
Answer
(i) A: Copper nitrate becomes a deep/inky blue colour when excess of ammonium hydroxide is added to it.
(ii) D: Lead nitrate gives a white precipitate with excess ammonium hydroxide solution.
From the list of substances given — Ammonium sulphate, Lead carbonate, Chlorine, Copper nitrate, Ferrous sulphate — State a solution of the compound which gives a dirty green precipitate with sodium hydroxide.
Answer
Ferrous sulphate gives a dirty green precipitate with sodium hydroxide.
Write a balanced equation for the reaction between aluminium oxide and sodium hydroxide solution.
Answer
Al2O3 + 2NaOH ⟶ 2NaAlO2 + H2O
Give one test to distinguish between the following:
Iron [III] chloride soln. and Copper chloride soln.
Answer
Ammonium hydroxide can be used to distinguish between the two. Iron [III] chloride soln. forms reddish brown ppt. of Fe(OH)3 which is insoluble in excess of ammonium hydroxide whereas copper chloride soln. forms a blue ppt. of Cu(OH)2 which is soluble in excess of ammonium hydroxide.
The salt which in soln. gives a pale green precipitate with NaOH solution and a white ppt. with BaCl2 soln. is :
Answer
Iron [II] sulphate gives a pale green precipitate with NaOH solution and a white ppt. with BaCl2 soln.
Find the odd one with reasons [valency is not a criterion] :
Answer
Mg(OH)2
Reason — All others are amphoteric hydroxides.
Identity the substance P based on the information given :
The deliquescent salt P, turns yellow on dissolving in water, and gives a reddish brown precipitate with sodium hydroxide solution.
Answer
Ferric chloride [Fe(Cl)3]
Give an equation for —
Answer
Select the correct answer from A, B, C —
A: Sodium hydroxide soln.
B: A weak acid
C: Dilute sulphuric acid.
The solution which with zinc sulphate solution will give a white precipitate.
Answer
A: Sodium hydroxide soln
Choose the correct answer :
Hydroxide of this metal is soluble in NaOH solution.
Answer
Lead
Sodium hydroxide solution is added to the solutions containing the ions mentioned in List 1.
List 1 —
The precipitates obtained are in list 2 —
A: Reddish brown
B: White insoluble in excess
C: Dirty green
D: White soluble in excess
E: White soluble in excess
F: Blue.
Match list 1 with list 2
Answer
| List 1 | List 2 |
|---|---|
| Pb2+ | D: White soluble in excess |
| Fe2+ | C: Dirty green |
| Zn2+ | E: White soluble in excess |
| Fe3+ | A: Reddish brown |
| Cu2+ | F: Blue |
| Ca2+ | B: White insoluble in excess |
Give balanced equations for —
(i) Zinc oxide dissolves in NaOH
(ii) Zinc is heated with NaOH solution
Answer
(i) ZnO + 2NaOH ⟶ Na2ZnO2 + H2O
(ii) Zn + 2NaOH ⟶ Na2ZnO2 + H2
Name: The gas evolved on reaction of aluminium with boiling concentrated caustic alkali solution.
Answer
Hydrogen gas
2Al + 2NaOH + 2H2O ⟶ 2NaAlO2 + 3H2
State one observation for:
Answer
Chalky white insoluble precipitate is obtained.
Pb(NO3)2 + 2NH4OH ⟶ 2NH4NO3 + Pb(OH)2 ↓
Reddish brown insoluble precipitate is obtained.
FeCl3 + 3NaOH ⟶ 3NaCl + Fe(OH)3 ↓
State two relevant observations for the reaction:
Ammonium hydroxide solution is added to copper (II) nitrate solution in small quantities and then in excess.
Answer
Two observations are:
State your observation: When excess sodium hydroxide is added to calcium nitrate solution.
Answer
White precipitate is obtained which is almost insoluble in excess of NaOH.
To a salt solution 'Y' a small quantity of NH4OH solution is added slowly and then in excess. A pale blue precipitate is formed which dissolves in excess to form a clear inky blue solution. Identify the positive ion in the salt 'Y'
Answer
Cu2+ ion.
State your observations when ammonium hydroxide solution is added drop by drop and then in excess to each of the following:
(i) copper sulphate solution
(ii) zinc sulphate solution.
Answer
(i) Pale blue precipitate of Cu(OH)2 is formed, which becomes deep blue when excess of ammonium hydroxide is added.
CuSO4 + 2NH4OH ⟶ (NH4)2SO4 + Cu(OH)2 ↓
Cu(OH)2 + (NH4)2SO4 + 2NH4OH [in excess] ⟶ 4H2O + [Cu(NH3)4]SO4
(ii) Gelatinous white precipitate of zinc hydroxide is formed which becomes colourless solution on adding excess of ammonium hydroxide.
ZnSO4 + 2NH4OH ⟶ (NH4)2SO4 + Zn(OH)2 ↓
Zn(OH)2 +(NH4)2SO4 + 2NH4OH [in excess] ⟶ 4H2O + [Zn(NH3)4]SO4
State one relevant observation – Action of sodium hydroxide solution on iron [II] sulphate solution.
Answer
A dirty green precipitate is formed which is insoluble in excess of sodium hydroxide solution.
How will you distinguish between — Ammonium Hydroxide & Sodium Hydroxide using CuSO4
Answer
CuSO4 forms a pale blue precipitate which is insoluble in excess of sodium hydroxide and with ammonium hydroxide it forms a pale blue precipitate which dissolves in excess of ammonium hydroxide and forms a deep/inky blue solution.
Choose the correct answer from the options given :
The salt solution which does not react with ammonium hydroxide is :
Answer
Calcium nitrate
Reason — concentration of OH1- ions is low and so ppt. cannot be formed.
Write a balanced chemical equation for :
(i) Reaction of sodium hydroxide solution with iron [III] chloride solution.
(ii) Reaction of zinc with potassium hydroxide solution.
Answer
(i) FeCl3 + 3NaOH ⟶ 3NaCl + Fe(OH)3
(ii) Zn + 2KOH ⟶ K2ZnO2 + H2
State one relevant observation : Lead nitrate solution is treated with sodium hydroxide soln. drop wise, till it is in excess.
Answer
Chalky white precipitate is formed which is soluble in excess of sodium hydroxide and forms a colourless solution.
Write balanced chemical equation for —
Ammonium hydroxide is added to ferrous sulphate solution.
Answer
2NH4OH + FeSO4 ⟶ (NH4)2SO4 + Fe(OH)2
Copper [II] sulphate solution reacts with NaOH solution to form a precipitate of Cu(OH)2. State it's colour.
Answer
Pale blue precipitate is formed.
State one relevant observation for the reaction : Addition of excess ammonium hydroxide into copper sulphate solution.
Answer
Deep blue or inky blue solution is formed when excess of ammonium hydroxide is added to copper sulphate solution.
Salts of ............... [normal/transitional] elements are generally coloured. From the ions K1+, Cr3+, Fe2+, Ca2+, SO32-, MnO41-, NO31- the ions generally coloured are ...............
Answer
Salts of transitional elements are generally coloured. From the ions K1+, Cr3+, Fe2+, Ca2+, SO32-, MnO41-, NO31- the ions generally coloured are Cr3+, Fe2+, MnO41- .
The hydroxide which is soluble in excess of NaOH is ............... [Zn(OH)2/Fe(OH)3/Fe(OH)2]
Answer
The hydroxide which is soluble in excess of NaOH is Zn(OH)2
The salt which will not react with NH4OH solution is ............... [ZnCl2/CuCl2/NH4Cl/FeCl2]
Answer
The salt which will not react with NH4OH solution is NH4Cl
The substance/s which react with hot conc. NaOH soln. and undergoes a neutralization reaction ............... [Al2O3/Al/Al(OH)3]
Answer
The substance/s which react with hot conc. NaOH soln. and undergoes a neutralization reaction Al2O3.
To distinguish soluble salts of zinc and lead, ............... [NaOH/NH4OH] can be used.
Answer
To distinguish soluble salts of zinc and lead NaOH can be used.
Oxides and hydroxides of certain metals i.e ............... [iron/ zinc/copper/aluminium/magnesium/lead] are amphoteric and react with ............... [acids/alkalis/acids and alkalis] to give salt and water.
Answer
Oxides and hydroxides of certain metals i.e zinc, aluminium, lead are amphoteric and react with acids and alkalis to give salt and water.
| Action of Sodium Hydroxide — on solutions of salts | Complete and balance the equations |
|---|---|
| 1a. Calcium nitrate and | Ca(NO3)2 + NaOH ⟶ ............... + ............... ↓ |
| 1b. Magnesium Chloride | MgCl2 + NaOH ⟶ ............... + ............... ↓ |
| 2. Iron [II] sulphate | FeSO4 + NaOH ⟶ ............... + ............... ↓ |
| 3. Iron [III] chloride | FeCl3 + NaOH ⟶ ............... + ............... ↓ |
| 4. Copper [II] sulphate | CuSO4 + NaOH ⟶ ............... + ............... ↓ |
| 5. Zinc sulphate | ZnSO4 + NaOH ⟶ ............... + ............... ↓ [Zn(OH)2 + NaOH [in excess] ⟶ ............... + ...............] |
| 6. Lead nitrate | Pb(NO3)2 + NaOH ⟶ ............... + ............... ↓ [Pb(OH)2 + NaOH [in excess] ⟶ ............... + ...............] |
Answer
| Action of Sodium Hydroxide — on solutions of salts | Complete and balance the equations |
|---|---|
| 1a. Calcium nitrate and | Ca(NO3)2 + 2NaOH ⟶ 2NaNO3 + Ca(OH)2 ↓ |
| 1b. Magnesium Chloride | MgCl2 +2NaOH ⟶ 2NaCl + Mg(OH)2 ↓ |
| 2. Iron [II] sulphate | FeSO4 + 2NaOH ⟶ Na2SO4 + Fe(OH)2 ↓ |
| 3. Iron [III] chloride | FeCl3 + 3NaOH ⟶ 3NaCl + Fe(OH)3 ↓ |
| 4. Copper [II] sulphate | CuSO4 + 2NaOH ⟶ Na2SO4 + Cu(OH)2 ↓ |
| 5. Zinc sulphate | ZnSO4 + 2NaOH ⟶ Na2SO4 + Zn(OH)2 ↓ [Zn(OH)2 + 2NaOH [in excess] ⟶ 2H2O + Na2ZnO2] |
| 6. Lead nitrate | Pb(NO3)2 + 2NaOH ⟶ 2NaNO3 + Pb(OH)2 ↓ [Pb(OH)2 + 2NaOH [excess] ⟶ 2H2O + Na2PbO2] |
| Action of Ammonium Hydroxide — on solutions of salts | |
|---|---|
| 7. Magnesium chloride | MgCl2 + NH4OH ⟶ ............... + ............... ↓ |
| 8. Iron [II] sulphate | FeSO4 + NH4OH ⟶ ............... + ............... ↓ |
| 9. Iron [III] chloride | FeCl3 + NH4OH ⟶ ............... + ............... ↓ |
| 10. Copper [II] sulphate | CuSO4 + NH4OH ⟶ ............... + ............... ↓ [Cu(OH)2 + (NH4)2SO4 + NH4OH [in excess] ⟶ ............... + ............... ] |
| 11. Zinc sulphate | ZnSO4 + NH4OH ⟶ ............... + ............... ↓ [Zn(OH)2 +(NH4)2SO4 + NH4OH [in excess] ⟶ ............... + ...............] |
| 12. Lead nitrate | Pb(NO3)2 + NH4OH ⟶ ............... + ............... ↓ |
Answer
| Action of Ammonium Hydroxide — on solutions of salts | |
|---|---|
| 7. Magnesium chloride | MgCl2 + 2NH4OH ⟶ 2NH4Cl + Mg(OH)2 ↓ |
| 8. Iron [II] sulphate | FeSO4 + 2NH4OH ⟶ (NH4)2SO4 + Fe(OH)2 ↓ |
| 9. Iron [III] chloride | FeCl3 + 3NH4OH ⟶ 3NH4Cl + Fe(OH)3 ↓ |
| 10. Copper [II] sulphate | CuSO4 + 2NH4OH ⟶ (NH4)2SO4 + Cu(OH)2 ↓ [Cu(OH)2 + (NH4)2SO4 + 2NH4OH [in excess] ⟶ 4H2O + [Cu(NH3)4]SO4] |
| 11. Zinc sulphate | ZnSO4 + 2NH4OH ⟶ (NH4)2SO4 + Zn(OH)2 ↓ [Zn(OH)2 +(NH4)2SO4 + 2NH4OH [in excess] ⟶ 4H2O + [Zn(NH3)4]SO4] |
| 12. Lead nitrate | Pb(NO3)2 + 2NH4OH ⟶ 2NH4NO3 + Pb(OH)2 ↓ |
| Action of Alkalis — on certain metals | |
|---|---|
| 13. Zinc | Zn + NaOH ⟶ ............... + ............... |
| 14. Zinc | Zn + KOH ⟶ ............... + ............... |
| 15. Lead | Pb + NaOH ⟶ ............... + ............... |
| 16. Lead | Pb + KOH ⟶ ............... + ............... |
| 17. Aluminium | Al + NaOH + H2O ⟶ ............... + ............... |
| 18. Aluminium | Al + KOH + H2O ⟶ ............... + ............... |
Answer
| Action of Alkalis — on certain metals | |
|---|---|
| 13. Zinc | Zn + 2NaOH ⟶ Na2ZnO2 + H2 |
| 14. Zinc | Zn + 2KOH ⟶ K2ZnO2 + H2 |
| 15. Lead | Pb + 2NaOH ⟶ Na2PbO2 + H2 |
| 16. Lead | Pb + 2KOH ⟶ K2PbO2 + H2 |
| 17. Aluminium | 2Al + 2NaOH + 2H2O ⟶ 2NaAlO2 + 3H2 |
| 18. Aluminium | 2Al + 2KOH + 2H2O ⟶ 2KAlO2 + 3H2 |
| Action of Alkalis — on oxides and hydroxides of certain metals | |
|---|---|
| 19. Zinc oxide | ZnO + NaOH ⟶ ............... + ............... |
| 20. Zinc hydroxide | Zn(OH)2 + NaOH ⟶ ............... + ............... |
| 21. Lead [II] oxide | PbO + NaOH ⟶ ............... + ............... |
| 22. Lead hydroxide | Pb(OH)2 + NaOH ⟶ ............... + ............... |
| 23. Aluminium oxide | Al2O3 + NaOH ⟶ ............... + ............... |
| 24. Aluminium hydroxide | Al(OH)3 + KOH ⟶ ............... + ............... |
Answer
| Action of Alkalis — on oxides and hydroxides of certain metals | |
|---|---|
| 19. Zinc oxide | ZnO + 2NaOH ⟶ Na2ZnO2 + H2O |
| 20. Zinc hydroxide | Zn(OH)2 + 2NaOH ⟶ Na2ZnO2 + 2H2O |
| 21. Lead [II] oxide | PbO + 2NaOH ⟶ Na2PbO2 + H2O |
| 22. Lead hydroxide | Pb(OH)2 + 2NaOH ⟶ Na2PbO2 + 2H2O |
| 23. Aluminium oxide | Al2O3 + 2NaOH ⟶ 2NaAlO2 + H2O |
| 24. Aluminium hydroxide | Al(OH)3 + KOH ⟶ KAlO2 + 2H2O |