Frank Solutions for Chapter 4 Analytical Chemistry Class 10 Chemistry ICSE
1. Write the colour of the following salts:
(a) Cuprous salts.
(b) Cupric salts.
(c) Aluminium salts.
(d) Ferrous salts.
(e) Ferric salts.
(f) Calcium salts.
Answer
(a) Cuprous salts = Colourless
(b) Cupric salts = Blue
(c) Aluminium salts = Colourless
(d) Ferrous salts = Light green
(e) Ferric salts = Yellow
(f) Calcium salts = Colourless
2. Using ammonium hydroxide, how would you distinguish between the following pairs of ions in solution?
(a) Ferrous ion and Ferric ion.
(b) Zinc ion and Lead ion.
Answer
(a) Ferrous ion and Ferric ion.
(i) FeSO4 + 2NH4OH ⟶ Fe(OH)2 ↓+ (NH4)2SO4
Fe(OH)2 forms dirty green precipitates.
(i) Fe2(SO4)3 + 6NH4OH ⟶ 2Fe(OH)2 ↓ + 3(NH4)2SO4
Fe(OH)3 forms reddish brown precipitates.
(b) Zinc ion and Lead ion.
(i) ZnSO4 + 2NH4OH ⟶ Zn(OH)2 ↓ + (NH4)2SO4
Zn(OH)2 forms white gelatinous precipitates. In the presence of excess of ammonium hydroxide these precipitates get dissolved .
(ii) Pb(NO3)2 + 2NH4OH ⟶ Pb(OH)2 ↓ + 2NH4OH
Pb(OH)2 forms white precipitates. This precipitate is insoluble in the presence of excess of ammonium hydroxide Concept Insight: Ammonium hydroxide forms insoluble hydroxides when treated with certain metallic salt solutions. The insoluble hydroxides thus formed get precipitated in the form of a precipitate and may be identified by their distinct colours.
3. You are provided with PbCO3, ZnCO3 and CaCO3. How will you identify these cations?
Answer
By use of Ammonium hydroxide we can identify the ions PbCO3, ZnCO3 and CaCO3 as :
(i) PbCO3 + 2NH4OH → Pb(OH)2 ↓ + 2NH4NO3
Pb(OH)2 forms white precipitate which are insoluble in excess ammonium hydroxide.
(ii) ZnCO3 + NH4OH → Zn(OH)2 ↓ + 2Na2CO3
Zn(OH)2 forms white gelatinous precipitate which are soluble in excess ammonium hydroxide.
(iii) CaCO3 + NH4OH → Ca(OH)2 + 2Na2CO3
No precipitation of Ca(OH)2 occurs even with addition of excess of NH4OH.
Because the concentration of hydroxide ion from ammonium hydroxide is so low that it cannot precipitate the hydroxide of calcium.
Concept Insight : Some precipitated metallic hydroxides by ammonium hydroxide become soluble hydroxides when treated with excess of ammonium hydroxide due to the formation of a soluble complex salt in the presence of excess of ammonium hydroxide.
4. Z is a compound. With dilute HCl it gives a gas turning dichromatic solution green. Z gives lilac flame. Name Z.
Answer
K2SO4.
5. What do you observe when caustic soda solution is added to the following solution: first a little and then in excess
(a) FeCl3
(b) ZnSO4
(c) Pb(NO3)2
(d) CuSO4
Answer
(a) Addition of caustic soda to FeCl3 solution :
FeCl3 + 3NaOH ⟶ Fe(OH)3 ↓ + 3NaCl
[Fe(OH)3 :Reddish Brown ppt.]
(b) Addition of caustic soda to ZnSO4 solution :
ZnSO4 + 2NaOH ⟶ Zn(OH)2 ↓ + Na2SO4
[Zn(OH)2 :White gelatinous ppt.]
(c) Addition of caustic soda to Pb(NO)3 solution:
Pb(NO)3 + 2NaOH ⟶ Pb(OH)2 ↓ + 2NaNO3
[Pb(OH)2 :White ppt.]
(d) Addition of caustic soda to CuSO4 + 2NaOH ⟶ Cu(OH)2 ↓ + Na2SO4
[Cu(OH)2 :Pale blue ppt.]
6. What is the reaction of freshly precipitated aluminium hydroxide with caustic soda solution? Give equation.
Answer
The reaction of freshly precipitated aluminium hydroxide with caustic soda solution is as :
Al(OH)3 + NaOH ⟶ NaAlO2 + 2H2O
[NaAlO2 :Sodium aluminate (White)]
7. What do you understand by amphoteric oxide? Give the balanced equations for the reaction with three different amphoteric oxides with a caustic alkali. Write your observation if any.
Answer
Amphoteric oxides : amphoteric oxides are those compounds, which react with both acids and alkalis to form salt and water.
For example: Oxides of Aluminium, zinc and lead are amphoteric in nature.
Balanced equations for the reaction of different amphoteric oxides with a caustic alkali :
Amphoteric oxide + Alkali ⟶ Salt + water 
8. Name a solution that will separate the components of the following mixtures:
(a) Zn(OH)2 from Pb(OH)2
(b) CaO from PbO
(c) CuO from ZnO
Answer
(a) Zn(OH)2 from Pb(OH)2: Ammonium hydroxide (NH4OH) solution can separate Zn(OH)2 from Pb(OH)2 as Zn(OH)2 precipitates are dissolved in excess of NH4OH solution while Pb(OH)2 precipitates are insoluble in excess of NH4OH solution.
(b) CaO from PbO: Sodium hydroxide solution can separate CaO from PbO as CaO precipitates are sparingly soluble in excess of NaOH solution while PbO precipitates are soluble in excess of NaOH solution.
(c) CuO from ZnO: Sodium hydroxide solution can separate CuO from ZnO as CuO precipitates remains insoluble in excess of NaOH solution while ZnO precipitates are soluble in excess of NaOH solution.
9. Give two examples of amphoteric hydroxides.
Answer
Examples of amphoteric hydroxides are: Zn(OH)2, Al(OH)3.
10. A metal whose alloy finds use in the construction of aircrafts in the powdered form is added to sodium hydroxide solution. A colourless gas was evolved and after reaction was over, the solution was colourless.
(a) Name the powdered metal added to sodium hydroxide solution.
(b) Name the gas evolved.
(c) Name the salt present in the colorless solution.
Answer
(a) The powdered metal added to sodium hydroxide solution is Aluminium.
(b) The gas evolved is hydrogen.
(c) The salt present in the colorless solution is sodium aluminate (NaAlO2).
Concept Insight : The alloy of aluminium metal i.e. duraluminium finds use in the construction of aircrafts. Reaction of aluminium metal with sodium hydroxide is as :
2Al + 2NaOH + 2H2O ⟶ 2NaAlO2 + 3H2
11. Name:
(a) A metallic hydroxide soluble in excess of NH4OH
(a) A metallic oxide soluble in excess of caustic soda solution.
(b) A strong alkali
(c) A weak alkali.
(d) Two coloured ions
(e) Two bases which are not alkalis but dissolve in strong alkalis.
(f) A coloured metallic oxide which dissolves in alkalis to yield colourless solutions.
Answer
(a) Zn(OH)2
(b) Na2O.
(c) NaOH
(d) NH4OH
(e) Cu2+ , Mn2-
(f) Zn(OH)2 and Pb(OH)2
(g) PbO
12. What happens when ammonia solution is added
(a) Dropwise and then
(b) In excess to the following solutions:
(i) CuSO4
(ii) ZnSO4
(iii) FeCl3
(c) Write balanced reactions.
Answer
13. Name the chloride of a metal which is soluble in excess of ammonium hydroxide.
Answer
The chloride of a metal which is soluble in excess of ammonium hydroxide is zinc chloride i.e. ZnCl2.
14. On adding dilute ammonia solution to a colourless solution of a salt, a white gelatinous precipitate appears. This precipitate however dissolves on addition of excess of ammonia solution. Identify (Choose from Na, l, Zn, Pb, Fe)
(a) Which metal salt solution was used?
(b) What is the formula of white gelatinous precipitate obtained?
Answer
(a) Zinc (Zn) metal salt solution was used.
(b) The formula of white gelatinous precipitate is Zn(OH)2.
15. Name
(a) A yellow monoxide that dissolves in hot and concentrated caustic alkali.
(b) A white, insoluble oxide that dissolves when fused with caustic soda or potash.
(c) A compound containing zinc in the anion.
Answer
(a) PbO
(b) Al2O3
(c) Na2ZnO2
16. Fill in the blanks:
(a) Salts of ______ [normal / transition] elements are generally coloured. From the ions K1+, Cr3+, Fe2+, Ca2+, the ions generally coloured are ______.
(b) The hydroxide which is soluble in excess of NaOH is ______ [Zn(OH)2 / Fe(OH)3 / Fe(OH)2].
(c) The salt which will not react with NH4OH solution ______[ZnCl2, CuCl2 / NH4Cl/ FeCl2]
(d) The substance/s which react with hot conc. NaOH solution and undergoes a neutralization reaction ______ [Al2O3 / Al / Al(OH)3]
(e) To distinguish soluble salts of zinc and lead ______ [NaOH / NH4OH]can be used.
Answer
(a) transition, Cr3+, Fe2+, MnO44-.
(b) Zn(OH)2
(c) NH4Cl
(d) Al2O3, Al
(e) NH4OH
17. Choose the correct answer from the options given below :
(i) Color of ferrous ion is
(a) Blue
(b) Green
(c) Pink
(d) Light green
Answer
(b) Green
(ii) Which one is colourless anion?
(a) HCO3
(iii) Sodium zincate (Na2ZnO2) is
(a) Pale blue ppt
(b) Reddish brown ppt
(c) Colourless
(d) Dirty green ppt
(c) Colourless
(a) N2
(b) H2
(c) H2O
(d) OH
(a) Iron (II) salts
(b) Iron (III) salts
(c) Lead salts
(d) Copper (II) salts
Answer
(v) Copper(II) salts
18. You are given a mixture of precipitated copper hydroxide and zinc hydroxide. Name a solvent which will dissolve:
(a) Only copper hydroxide
(b) Only zinc hydroxide
(c) Both copper hydroxide and zinc hydroxide
Answer
(a) Addition of KCN
(b) Addition of excess of NaOH.
(c) Addition of excess of NH4OH.
19. Using sodium hydroxide solution, how will you distinguish:
(a) Zinc nitrate solution from calcium nitrate solution
(b) Iron (II) chloride from iron (III) chloride
(c) Lead hydroxide from magnesium hydroxide.
Answer
(a) Zinc nitrate solution from calcium nitrate solution :
(i) Zn(NO3) + 2NaOH ⟶ Zn(OH)2 + 2NaNO3
On further addition of NaOH, Zn(OH)2 dissolves.
(ii) Ca(NO3)2 + 2NaOH ⟶ Ca(OH)2 + 2NaNO3
Ca(OH)2 precipitates are sparingly soluble in excess of sodium hydroxide.
(b) Iron (II) chloride from iron (III) chloride
(i) FeCl2 + 2NaOH — Fe(OH)2 + 2NaCI
Fe(OH)2 precipitates are dirty green gelatinous in nature.
(ii) FeCl3 + 3NaOH — Fe(OH)2 + 3NaCI
Fe(OH)3 precipitates are reddish brown in colour.
(c) Lead hydroxide from magnesium hydroxide
When sodium hydroxide is added, lead hydroxide is dissolved in it but when sodium hydroxide is added to magnesium hydroxide, there is no visible reaction i.e. it remains insoluble.
20. (a) Sodium hydroxide solution is added to solution A. A white precipitate is formed which is soluble in excess sodium hydroxide. Name the metal ion present in A.
(b) When ammonium hydroxide is added to solution B, a pale blue precipitate is formed. This pale blue precipitate dissolves in excess ammonium hydroxide to give an inky blue solution. Name the cation present in solution B. What is the probable colour of solution B?
Answer
(a) The metal ion present in solution A is Pb2+.
(b) The cation present in solution B is Cu2+. The probable colour of solution B is blue.
21. What do you see when sodium hydroxide solution is added to zinc sulphate solution, till it is in excess?
Answer
When sodium hydroxide solution is added to zinc sulphate solution, till it is in excess white gelatinous precipitates of Zn(OH)2 are formed and due to the excess of sodium
hydroxide these ppt. get dissolved immidiately :
ZnSO4 + 2NaOH ⟶ Zn(OH)2 + Na2SO4
[Zn(OH)2 :White gelatinous ppt.]
Zn(OH)2 + 2NaOH ⟶ Na2ZnO2 + 2H2O
[Na2ZnO2 :colourless]
22. You are given three white powders-calcium carbonate, lead carbonate and zinc carbonate. Describe the tests you would carry out in solution, to identify the metal ion in each of the above compounds. Indicate clearly how you would prepare the solutions for the tests.
Answer
The solutions for the tests will be prepared by dissolving the given powders separately in water.
- Solution of Calcium carbonate:
Calcium carbonate is CaCO3 and contains Ca2+ ions. Sodium hydroxide solution NaOH can be used to identify Ca2+ since its addition to calcium carbonate solution will give white precipitates of Ca(OH)2 which are sparingly soluble in excess of NaOH. - (ii) Solution of Lead carbonate:
Lead carbonate is PbCO3 and contains Pb2+ ions. Ammonium hydroxide solution NH4OH can be used to identify Pb2+ since its addition to lead carbonate solution will give white precipitates of Pb(OH)2 which are insoluble in excess of NH4OH. - Solution of Zinc carbonate:
Zinc carbonate is ZnCO3 and contains Zn2+ ions. Sodium hydroxide solution NaOH can be used to identify Zn2+ since its addition to zinc carbonate solution will give white gelatinous precipitates of Zn(OH)2 which are soluble in excess of NaOH.
23. Write equation for the reaction that will take place when copper sulphate solution is added to sodium hydroxide solution.
Answer
For the reaction that will take place when copper sulphate solution is added to sodium hydroxide solution the equation is as :
CuSO4 + 2NaOH ⟶ Cu(OH)2 + Na2SO4
24. Three test tubes contain calcium nitrate solution, zinc nitrate solution and lead nitrate solution. Each solution is divided into two portions (i) and (ii). Describe the effect of
(i) Adding sodium hydroxide solution to each portion in turn till it is in excess.
(ii) Adding ammonium hydroxide to each portion in turn till it is in excess.
Answer
(i) Sodium Hydroxide
|
|
Small amount |
In excess |
|
Calcium nitrate |
White precipitate |
Sparingly soluble |
|
Zinc nitrate |
White precipitate |
Soluble |
|
Lead nitrate |
White precipitate |
Soluble |
(ii) Ammonium Hydroxide
|
|
Small amount |
In excess |
|
Calcium nitrate |
No visible reaction |
No change |
|
Zinc nitrate |
White precipitate |
Soluble |
|
Lead nitrate |
White precipitate |
Soluble |
25. (a) Sodium hydroxide solution can be used to distinguish between i. iron (II) sulphate solution and (ii) iron (III) sulphate solution; because these solutions give different coloured precipitates with sodium hydroxide solution. Give the colour of the precipitate formed with each of the solution.
(b) What will you observe when barium chloride solution is added to iron(II) sulphate solution.
(c) How will the action of dilute hydrochloric acid on sodium carbonate and sodium sulphite enables you to distinguish between these two compounds?
Answer
(a) Sodium hydroxide solution gives dirty green coloured precipitates with iron(II) sulphate solution.
With iron(III) sulphate solution sodium hydroxide solution gives reddish brown precipitates.
(b) When barium chloride solution is added to iron(II) sulphate solution it gives white precipitate of BaSO4 .
(c) Sodium carbonate + hydrochloric acid = sodium chloride + water + carbon dioxide
NaCO3 + HCI ⟶ NaCI + H2O + CO2
Sodium sulphite + hydrochloric acid — sodium chloride + water + hydrogen sulphide
2Na2SO3 - 4HCI → 4NaCl + 6H2O + 2H2S
Production of Foul smelling hydrogen sulphide gas will easily help to distinguish between sodium carbonate and sodium sulphite.
26. Describe in each case, one chemical test that would enable you to distinguish between the following pairs of chemicals. Describe what happens with each chemical or state 'no visible reaction'.
(i) Sodium chloride solution and sodium nitrate solution.
(ii) Sodium sulphate solution and sodium chloride solution.
(iii) Calcium nitrate solution and zinc nitrate solution.
Answer
(i) Sodium chloride solution and sodium nitrate solution.
Add freshly prepared ferrous sulphate solution to the two solutions. Then by the side of the test tube, pour concentrated sulphuric acid to each slowly. The one in which brown ring appears is sodium nitrate solution while the other is sodium chloride solution. (ii) Sodium sulphate solution and sodium chloride solution.
|
Sodium sulphate solution |
Sodium chloride solution |
|
When Sodium sulphate solution is treated with Barium chloride solution, a white precipitate is formed which is insoluble in all the mineral acids. |
When Sodium chloride solution is treated with Barium chloride solution, no visible reaction is observed. |
- ZnNO3 + 2NaOH ⟶ Zn(OH)2 + NaNO3
On further addition of NaOH, Zn(OH)3 dissolves. - Ca(NO3)2 + 2NaOH → Ca(OH)2 + 2NaNO3
Ca(OH)2 precipitates are sparingly soluble in excess of sodium hydroxide.
27. Write balanced equations for the following reactions:
(i) Iron(II) chloride solution with sodium hydroxide solution.
(ii) Chlorine and cold dilute sodium hydroxide solution.
(iii) Zinc and sodium hydroxide solution
(iv) Sulphur dioxide and sodium hydroxide solution
(Give the equation for the formation of the normal salt)
Answer
(i) FeCl2 + 2NaOH → Fe(OH)2 + 2NaCl
(ii) 2NaOH + Cl2 → NaCl + NaOCl + H2O
(iii) Zn + 2NaOH → Na2ZnO2 + H2
(iv) SO2 + 2NaOH → Na2SO3 + H2O
28. State what do you observe when:
(i) Neutral litmus solution is added to alkaline solution
(ii) Ammonium hydroxide is added to iron (III) sulphate solution.
(iii) Lead nitrate and sodium chloride are mixed.
(iv) Ethane is bubbled through a solution of bromine in tetrachloromethane (carbon tetra chloride).
(v) Sulphur burns.
Answer
(i) Neutral litmus solution turns blue n colour when added to alkaline solution.
(ii) Fe2(SO4)3 + 6NH4OH → 2Fe(OH)3 + 3(NH4)2SO4
[Fe2(SO4)3 :Yellow, Fe(OH)3 :Reddish brown]
(iii) Pb(NO3)2 + 2NaCl ⟶ PbCl2 + 2NaNO3
(iv) Nothing is observed since ethane is a saturated hydrocarbon.
(v) Sulfur burns with a blue flame concomitant with formation of sulfur dioxide, notable for its peculiar suffocating odor.
29. (i) How would you distinguish between Zn2+ and Pb2+ ions, using ammonium hydroxide solution ?
(ii) Copy and complete the following table which refers to the action of heat on some carbonates :
|
Carbonate |
Colour of residue on cooling |
|
Zinc carbonate |
|
|
Lead carbonate |
|
|
Copper carbonate |
|
Answer
(i) Zn2+ ions on addition of NH4OH forms white precipitates of Zn(OH)2 which further dissolves in excess of NH4OH.
(ii)
|
Carbonate |
Colour of residue on cooling |
|
Zinc carbonate |
White amorphous powder |
|
Lead carbonate |
yellow |
|
Copper carbonate |
Bluish green crystalline solid |
30. Write the observations, and balanced equations for the following reactions:
(i) Sodium hydroxide is added dropwise to a solution of zinc sulphate, till it is in excess.
(ii) Ammonium hydroxide is added first in a small quantity, and then in excess, to a solution of copper sulphate.
(iii) Excess of ammonium hydroxide is added to a substance, obtained by adding hydrochloric acid to silver nitrate solution.
(iv) Moist starch iodide paper is placed at the mouth of a test tube containing chlorine gas.
(v) A paper dipped in potassium permanganate solution is placed at the mouth of a test tube, containing sulphur dioxide gas.
Answer
(i) Sodium hydroxide when added to zinc sulphate gives gelatinous white precipitate which dissolves in excess of sodium hydroxide.
ZnSO4 + 2NaOH ⟶ Zn(OH)2 + Na2SO4
Zn(OH)2 + 2NaOH ⟶ Na2ZnO2
(ii) When ammonium hydroxide is added in small quantity to copper sulphate solution; it gives blue precipitate of Cu(OH)2
CuSO4 + 2NH4OH ⟶ Cu(OH)2 + (NH4)2SO4
When ammonium hydroxide is added in excess, the blue precipitate dissolves giving deep blue solution of tetra amine copper sulphate.
Cu(OH)2 + (NH4)2SO4 + 2NH4OH ⟶ [Cu(NH3)4SO4 + 4H4O
[In excess Tetrammine, Copper(II) Sulphate (Deep blue solution)]
(iii) Curdy white precipitate of AgCl formed by reaction between hydrochloric acid and silver nitrate solution, dissolves in excess of NH4OH.
AgNO3 + HCI ⟶ AgCl + HNO3
AgC1+ 2NH4OH ⟶ Ag(NH3)2CI + 2H2O
(iv) Starch paper turns blue black:
2KI +Cl2 ⟶ 2KCl + I2
I2 reacts with starch to give blue black colour.
The chlorine liberates iodine from KI and then it is decolourised.
(v) Pink colour of KMnO4 is discharged.
2KMnO4 + 3H2SO4 ⟶ K2SO4 + 2MnSO4 + 50 + 3H2O ...(1)
SO2 + H2O + O ⟶ H2SO4 × 5 ....(2)
31. 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 precipiatate (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 |
|
|
Answer
|
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 |
Blue |
Insoluble |
32. The questions (i) to (v) refer 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 two solutions will give a white precipitate when treated with dilute hydrochloric acid followed by barium chloride solution/
(ii) Which two solutions will give a white precipitate when treated with dilute nitric acid followed by silver nitrate solution?
(iii) Which solution will give a white precipitate when either dilute hydrochloric acid or dilute sulphuric acid is added to it?
(iv) Which solution becomes a deep/inky blue colour when excess of ammonium hydroxide is added to it?
(v) Which solution gives a white precipitate with excess ammonium hydroxide?
Answer
(i) B and E (Iron (II) sulphate and Magnesium sulphate)
(ii) C and F (Iron (III) chloride and Zinc chloride)
(iii) D (Lead nitrate)
(iv) A (Copper nitrate)
(v) F (Zinc chloride)
33. Match the following :
|
Column A |
Column B |
|
1. A substance that turns moist starch iodide paper blue. |
A. Ammonium sulphate B. Lead carbonate C. Chlorine D. Copper nitrate
|
Answer
|
Column A |
Column B |
|
1. A substance that turns moist starch iodide paper blue. |
C. Chlorine
A. Ammonium hydroxide. B. Lead carbonate
|
The metal oxide which can react with acid as well as alkali is:
(a) Silver oxide.
(b) Copper (II) oxide.
(c) Aluminium oxide
(d) Calcium oxide
Answer
C (Aluminium oxide)
35. Identify the substances P, Q and R in each case based on the information given below:
(i) The deliquescent salt P, turns yellow on dissolving in water, and gives a reddish
brown precipitate with sodium hydroxide solution.
(ii) The white crystalline solid Q is soluble in water. It liberates a pungent smelling gas when heated with sodium hydroxide solution.
(iii) The pale green solid R turns reddish brown on heating. Its aqueous solution gives a white precipitate with barium chloride solution. The precipitate is insoluble in mineral acids.
Answer
(i) P is Ferric chloride
(ii) Q is an ammonium salt
(iii) R is ferrous sulphate
36. Give one chemical test to distinguish between the following pairs of compounds:
(i) Zinc sulphate solution and Zinc chloride solution.
(ii) Iron (II) chloride solution and iron (III) chloride solution.
Answer
(i) When BaCl2 solution is added to the given solution ZnSO4 gives a white precipitate while no precipitate is obtained with ZnCl2 solution.
(ii) When NaOH solution is added to the given solution, iron (II) chloride gives dirty green precipitate while reddish brown precipitate is obtained with iron(III) chloride.
37. From the list given below, select the word (s) required complete the blanks (i) to (v) in the following passage :
Note : words chosen from the list are to be used only once. Write only the answers. Do not copy the passage, [ reddish brown, ammonium, nitrogen dioxide, hydroxyl, dirty green, ammonia, acidic, alkaline]
Nitrogen and hydrogen combine in the presence of a catalyst to give (i) ________ gas. When the above mentioned gas is passed through water it forms a solution which will be (ii) ______ in nature and the solution contains (iii) ______ ions and (iv) _______ions. The above solution when added to iron (II) sulphate solution gives a (v) _________coloured precipitate of iron (II) hydroxide
Answer
(i) Ammonia
(ii) Alkaline
(iii) Ammonium
(iv) Hydroxyl
(v) Dirty green
38. Write the equation for the following reaction :
Zinc oxide is treated with sodium hydroxide solution.
Answer
ZnO + 2NaOH ⟶ Na2ZnO2 + H2O
39. Choose the correct answer from the options given below :
(i) Hydroxide of this metal is soluble is sodium hydroxide solution
(a) Magnesium
(b) Lead
(c) Silver
(d) Copper
(ii) When dilute sulphuric acid reacts with iron sulphide, the gas evolved is _______
(a) Hydrogen sulphide
(b) Sulphur dioxide
(c) Sulphur trioxide
(d) Vapour of sulphuric acid
Answer
(i) Lead
(ii) Hydrogen sulphide
40. State two relevant observations for each of the following:
(i) Ammonium hydroxide solution is added to copper (II) nitrate solution in small quantities and then in excess
(ii) Ammonium hydroxide solution is added to zinc nitrate solution in minimum quantities and then in excess
Answer
(i) (a) When NH4OH is added to copper (II) nitrate solution in small quantities, a pale blue precipitate is observed.
(b) When added in excess, NH4OH dissolves to give an inky blue solution forming a complex salt.
(ii) (a) When NH4OH is added to zinc nitrate solution in minimum quantity, it forms a gelatinous white precipitate.
(b) When added in excess, it dissolves to form a complex salt.
41. Distinguish between the following pairs of compound using the test give within brackets.
(i) Iron (II) Sulpate an and iron(III) using ammonium hydroxide)
(ii) A lead salt and a zinc salt (using excess ammonium hydroxide
Answer
(ii) Pb(NO3)2+2 NH4OH → Pb(OH)2+2NH4NO3
On adding excess of NH4OH, chalky white ppt. of insoluble Pb(OH)2 is formed.
ZnSO4 + 2NH4OH → Zn(OH)2 + (NH4)2SO4
With excess of NH4OH, white gelatinous ppt. of soluble Zn(OH)2 is formed.
42. State your observations when ammonium hydroxide solution is added drop by drop and then in excess to each of the following solutions :
(i) Copper sulphate solution
(ii) Zinc sulphate solution
Answer
(i) When NH4OH is added to copper sulphate solution drop-wise, a pale blue ppt. is obtained.
CuSO4 + 2NH4OH → Cu(OH)2 + (NH4)2SO4 + 4H2O
With excess of NH4OH, the ppt. dissolves to give a deep blue solution of tetra amine copper (II) sulphate.
Cu(OH)2 + (NH4)2SO4 + NH4OH → [Cu(NH3)4]SO4 + H2O
(ii) When NH4OH is added to zinc sulphate solution drop-wise, a white, gelatinous ppt. is obtained.
ZnSO4 + 2NH4OH → Zn(OH)2 + (NH4)2SO4
With an excess of NH4OH, the ppt. dissolves to give a colourless solution of tetra amine zinc (II) sulphate.
Zn(OH)2 + (NH4)2SO4 + 2NH4OH → [Zn(NH3)4]SO4 + 4H2O
43. Fill in the blank from the choices given in bracket.
Potassium sulphite on reacting with hydrochloric acid releases ______
Answer
Potassium sulphite on reacting with hydrochloric acid releases sulphur dioxide.
44. Choose the correct answer from the options given below :
A chloride which forms a precipitate that is soluble in excess of ammonium hydroxide is :
(a) Calcium chloride
(b) Ferrous chloride
(c) Ferric chloride
(d) Copper chloride
Answer
Copper chloride