Chemistry
Distinguish by a chemical test :
(a) Sodium carbonate and sodium sulphite
(b) Sodium chloride and sodium sulphide
(c) Sodium hydroxide solution and ammonium hydroxide solution.
(d) Ammonium sulphate and sodium sulphate.
(e) Sulphuric acid from nitric acid and hydrochloric acid.
Practical Chemistry
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Answer
(a) When dil. sulphuric acid is added to sodium carbonate and heated, colourless, odourless gas is evolved which turns lime water milky and has no effect on KMnO4 or K2Cr2O7 solutions.
When dil. sulphuric acid is added to sodium sulphite and heated, colourless gas with suffocating odour is evolved which turns lime water milky. It turns acidified K2Cr2O7 from orange to clear green and pink coloured KMnO4 to clear colourless.
Hence, the two compounds can be distinguished.
(b) When dil. sulphuric acid is added to sodium sulphide and heated, hydrogen sulphide gas is evolved which has the smell of rotten eggs and turns lead acetate paper black.
Whereas, when conc. sulphuric acid is added to sodium chloride and heated, HCl gas is evolved which gives dense white fumes when a glass rod dipped in ammonia is brought near it.
(c) When ammonium hydroxide is reacted with a solution of copper sulphate, a pale blue ppt. of copper hydroxide is formed which dissolves in excess of ammonium hydroxide forming a deep blue solution of a soluble complex salt [Cu(NH3)4]SO4 [tetramine copper [II] sulphate] .
CuSO4 + 2NH4OH ⟶ (NH4)2SO4 + Cu(OH)2 ↓
Cu(OH)2 + (NH4)2SO4 + 2NH4OH ⟶ [Cu(NH3)4]SO4 + 4H2O
Whereas, when copper sulphate is added to sodium hydroxide solution, pale blue ppt. of copper hydroxide is obtained which is insoluble in excess of sodium hydroxide.
CuSO4 + 2NaOH ⟶ Na2SO4 + Cu(OH)2 ↓
(d) When ammonium sulphate is heated with NaOH, ammonia gas is produced which turns red litmus blue whereas, sodium sulphate does not react with sodium hydroxide.
(NH4)2SO4 + 2NaOH ⟶ Na2SO4 + 2H2O + 2NH3
Na2SO4 + NaOH ⟶ no reaction.
(e) Barium chloride reacts with dil H2SO4 to form a white ppt. of barium sulphate.
BaCl2 + H2SO4 [dil.] ⟶ 2HCl + BaSO4 ↓ [white ppt.]
Whereas, HCl and nitric acid does not form a white ppt.
BaCl2 + HCl ⟶ No white ppt.
BaCl2 + HNO3 ⟶ No white ppt
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Question 2
Give a chemical test to distinguish between :
(a) Sodium chloride soln. and sodium nitrate soln.
(b) Hydrogen chloride gas and hydrogen sulphide gas.
(c) Calcium nitrate soln. and zinc nitrate soln.
(d) Carbon dioxide gas and sulphur dioxide gas.
(e) Sodium carbonate and sodium sulphite
(f) Ferrous nitrate and lead nitrate.
(g) Manganese dioxide and copper (Il) oxide.
(h) Sodium nitrate and sodium sulphite [using dilute sulphuric acid].
(i) Sodium chloride and sodium sulphide
(j) Sodium hydroxide solution and ammonium hydroxide solution.
(k) Ammonium sulphate and sodium sulphate.
(l) Sulphuric acid from nitric acid and hydrochloric acid.
(m) Magnesium chloride and magnesium nitrate solution
(n) Zinc sulphate solution and zinc chloride solution
(o) Iron (II) chloride soln. and iron (III) chloride soln.
(p) Calcium nitrate soln. and calcium chloride soln.