Chemistry
Identify the cation present in each of the following compounds — W, X, Y, Z :
(i) To solution 'W', ammonium hydroxide is added in minimum quantity first and then in excess. A dirty white precipitate is formed which dissolves in excess to form a clear solution.
(ii) To solution 'X' ammonium hydroxide is added in minimum quantity first and then in excess. A pale blue precipitate is formed which dissolves in excess to form a clear inky blue solution.
(iii) To solution 'Y' a small amount of sodium hydroxide is added slowly and then in excess. A white insoluble precipitate is formed.
(iv) To salt 'Z' - Ca(OH)2 soln. is added and heated. A pungent smelling gas turning moist red litmus paper blue is obtained.
Practical Chemistry
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Answer
(i) Zn2+ (Zinc Ion)
ZnSO4 + 2NH4OH ⟶ (NH4)2SO4 + Zn(OH)2 ↓
Zn(OH)2 + (NH4)2SO4 + 2NH4OH [in excess] ⟶ 4H2O + [Zn(NH3)4]SO4
(ii) Cu2+ (Copper (II) Ion)
CuSO4 + 2NH4OH ⟶ (NH4)2SO4 + Cu(OH)2 ↓
Cu(OH)2 + (NH4)2SO4 + 2NH4OH [in excess] ⟶ 4H2O + [Cu(NH3)4]SO4
(iii) Ca2+ (Calcium Ion)
CaCl2 + 2NaOH ⟶ 2NaCl + Ca(OH)2 ↓
(iv) NH4+ (Ammonium Ion)
2NH4Cl + Ca(OH)2 ⟶ CaCl2 + 2H2O + 2NH3
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State one relevant observation : When hydrogen sulphide gas is passed through lead acetate solution.
Identify the anion present in each of the following compounds: A, B, C :
(i) Salt 'A' reacts with conc. H2SO4 producing a gas which fumes in moist air and gives dense fumes with ammonia.
(ii) Salt 'B' reacts with dil. H2SO4 producing a gas which turns lime water milky but has no effect on acidified potassium dichromate solution.
(iii) When barium chloride solution is added to salt solution. 'C' a white precipitate insoluble in dilute hydrochloric acid is obtained.
Identify the cations in each of the following cases :
(i) NaOH solution when added to the solution 'A' - gives a reddish brown precipitate.
(ii) NH4OH solution when added to the solution 'B' - gives a white ppt which does not dissolve in excess.
(iii) NaOH solution when added to the solution 'C' - gives a white ppt which is insoluble in excess.
Choose the correct answer from the options – A chloride which forms a precipitate that is soluble in excess of ammonium hydroxide, is :
- Calcium chloride
- Ferrous chloride
- Ferric chloride
- Copper chloride.