Chemistry Practical II — 2025 Past Questions

University of Ilorin CHM108: 47 questions.

Topics: Basic Laboratory Techniques and Data Recording, Preliminary Tests on Compounds, Laboratory Techniques and Data Collection, Functional Group and Confirmatory Tests, Solubility Tests

  1. What is the chemical formula of a compound containing Fe²⁺ and SO₄²⁻ ions?
    1. FeSO₄
    2. Fe₂(SO₄)₃
    3. Fe₂SO₄
    4. FeSO₃
  2. What is the purpose of decantation in qualitative analysis?
    1. To evaporate solvent from a solution
    2. To separate a liquid from a precipitate by gently pouring off the liquid
    3. To filter a solution through filter paper
    4. To dissolve a precipitate in acid
  3. What is the purpose of evaporating a solution to dryness in qualitative analysis?
    1. To increase the volume of the solution
    2. To dissolve more solute in the solvent
    3. To recover the dissolved solid from the solution for further testing
    4. To remove precipitates from the solution
  4. Which active group includes Pb²⁺, As³⁺, and Hg²⁺?
    1. Group I cations (HCl group)
    2. Group II cations (Acidic H₂S group)
    3. Group III cations (NH₄OH group)
    4. Group VI cations (Soluble group)
  5. Which Group I cation does NOT form a precipitate with H₂S in an acidic medium?
    1. Pb²⁺
    2. Ag⁺
    3. Hg₂²⁺
    4. All Group I cations do not precipitate with H₂S
  6. What anion is detected in Group VI during the confirmatory test?
    1. Cl⁻, Br⁻, and I⁻
    2. SO₄²⁻ and SO₃²⁻
    3. NO₃⁻ and NO₂⁻
    4. PO₄³⁻, BO₃³⁻, and F⁻
  7. Which Group III cation forms a green precipitate with NH₄OH (ammonium hydroxide)?
    1. Fe³⁺
    2. Al³⁺
    3. Cr³⁺
    4. Co²⁺
  8. What cation turns pink on reacting with rubeanic acid?
    1. Cu²⁺
    2. Ni²⁺
    3. Zn²⁺
    4. Co²⁺
  9. What is the mark allocated for effort in the qualitative analysis of Fe₂(SO₄)₃?
    1. 2 marks
    2. 2.5 marks
    3. 3 marks
    4. 4 marks
  10. What is the colour of magnesium sulphate (MgSO₄) in crystalline form?
    1. Blue
    2. White
    3. Green
    4. Colourless
  11. Which of the following are soluble salts?
    1. Amine salts only
    2. Ammonium salts only
    3. Alkali metal salts only
    4. All of the above — amine salts, ammonium salts, and alkali metal salts
  12. What is the chemical formula for a compound containing Fe³⁺ and SO₄²⁻ ions?
    1. FeSO₄
    2. Fe₂SO₄
    3. Fe₂(SO₄)₃
    4. Fe₃(SO₄)₂
  13. Evaporating a solution to dryness is used to precipitate which group of cations?
    1. Group I cations (Pb²⁺, Ag⁺, Hg₂²⁺)
    2. Group II cations (Cu²⁺, As³⁺, Hg²⁺)
    3. Group III cations (Fe³⁺, Al³⁺, Cr³⁺)
    4. Group VI cations (Mg²⁺, Na⁺, K⁺)
  14. Which of the following cations are all found in Group I?
    1. Pb²⁺, Hg²⁺, and Ag⁺
    2. Pb²⁺, Hg₂²⁺, and Ag⁺
    3. Cu²⁺, Pb²⁺, and Bi³⁺
    4. Fe³⁺, Al³⁺, and Cr³⁺
  15. If no precipitate forms with H₂S in an acidic medium, what does this indicate?
    1. Group I cations are absent
    2. Group III cations are absent
    3. Group II cations are absent
    4. Group VI cations are absent
  16. Which cations in Group VI are confirmed by a flame test, and what colours do they produce?
    1. Ca²⁺ (brick red) and Ba²⁺ (apple green)
    2. Na⁺ (golden yellow) and K⁺ (lilac)
    3. Cu²⁺ (blue-green) and Pb²⁺ (pale blue)
    4. Mg²⁺ (white) and Zn²⁺ (colourless)
  17. What is the chemical formula of a sample containing Fe²⁺ and SO₄²⁻ ions?
    1. Fe₂(SO₄)₃
    2. FeSO₄
    3. FeS
    4. Fe₂(SO₃)₃
  18. What is the purpose of decantation in qualitative analysis?
    1. To separate a liquid from a precipitate or sediment by gently pouring the liquid away
    2. To boil off all the solvent from a solution to recover a solid
    3. To separate two miscible liquids with different boiling points
    4. To neutralize an acidic solution before further testing
  19. What is the purpose of evaporating a solution to dryness in qualitative analysis?
    1. To recover the dissolved solid (solute) from a solution and test the residue for further analysis
    2. To measure the exact volume of the solvent in a mixture
    3. To increase the rate of precipitation of impurities in a base
    4. To separate a liquid from a heavy sediment without heating
  20. Which active group in qualitative analysis includes Pb²⁺, As³⁺, and Hg²⁺?
    1. Group I cations
    2. Group II cations
    3. Group III cations
    4. Group IV cations
  21. How are Group I cations separated in qualitative analysis, given they do not precipitate with H₂S in an acidic medium?
    1. Precipitation as chlorides using dilute HCl
    2. Precipitation as sulfides using H₂S
    3. Precipitation as hydroxides using NH₄OH
    4. Precipitation as carbonates using (NH₄)₂CO₃
  22. Which of the following anions is detected in Group VI during the confirmatory tests in qualitative analysis?
    1. Phosphate (PO₄³⁻)
    2. Sulfate (SO₄²⁻)
    3. Chloride (Cl⁻)
    4. Nitrate (NO₃⁻)
  23. Which Group III cation forms a green precipitate with NH₄OH (ammonium hydroxide)?
    1. Fe³⁺
    2. Cr³⁺
    3. Al³⁺
    4. Mn²⁺
  24. Which of the following cations forms a characteristic colored complex (often confused with a pink color) on reacting with reagents like rubeanic acid or dimethylglyoxime during qualitative analysis?
    1. Cu
    2. Ni
    3. Zn
    4. Co
  25. What is the mark allocated for effort in the practical qualitative analysis of an unknown salt like Fe₂(SO₄)₃?
    1. 2 marks
    2. 2.5 marks
    3. 3 marks
    4. 4 marks
  26. What is the colour of magnesium sulfate (MgSO₄) in its crystalline form?
    1. Blue
    2. White
    3. Green
    4. Colourless
  27. The following compounds and groups typically represent soluble salts in qualitative analysis EXCEPT:
    1. Amine
    2. Ammonium salt
    3. Alkali salt
    4. All of the above
  28. What is the chemical formula of a sample containing Fe³⁺ and SO₄²⁻ ions?
    1. FeSO₄
    2. Fe₂(SO₄)₃
    3. Fe₃(SO₄)₂
    4. FeS
  29. Evaporating a solution to dryness is a technique used to precipitate Group 6 cations. Which of the following sets of ions belongs to this group?
    1. Mg²⁺ and Na⁺
    2. Pb²⁺ and Ag⁺
    3. Fe³⁺ and Al³⁺
    4. Ca²⁺ and Ba²⁺
  30. Which of the following sets of cations are all found in Group 1 of qualitative analysis?
    1. Pb²⁺, Hg²⁺, and Ag⁺
    2. Cu²⁺, Bi³⁺, and Cd²⁺
    3. Fe³⁺, Al³⁺, and Cr³⁺
    4. Mg²⁺, Na⁺, and K⁺
  31. During qualitative analysis, if no precipitate forms upon the addition of H₂S in an acidic medium, which group of cations is confirmed to be absent?
    1. Group 1 cations
    2. Group 2 cations
    3. Group 3 cations
    4. Group 4 cations
  32. Which Group 6 cations are confirmed using a flame test, and what are their respective flame colors?
    1. Na⁺ (Golden Yellow) and K⁺ (Lilac)
    2. Mg²⁺ (Brick Red) and Ca²⁺ (Apple Green)
    3. Cu²⁺ (Blue-Green) and Ba²⁺ (Apple Green)
    4. Na⁺ (Lilac) and K⁺ (Golden Yellow)
  33. What characteristic color is imparted to a non-luminous flame by sodium ions (Na⁺)?
    1. Lilac
    2. Golden yellow
    3. Brick red
    4. Apple green
  34. During a flame test, which of the following cations produces a lilac (pale purple) flame?
    1. Potassium (K⁺)
    2. Calcium (Ca²⁺)
    3. Barium (Ba²⁺)
    4. Copper (Cu²⁺)
  35. What is the expected flame color for a sample containing barium ions (Ba²⁺)?
    1. Blue-green
    2. Brick red
    3. Apple green
    4. Crimson
  36. Which cation is responsible for giving a brick-red color in a flame test?
    1. Sr²⁺
    2. Ca²⁺
    3. Mg²⁺
    4. Pb²⁺
  37. In an aqueous solution, what is the typical color of hydrated copper(II) ions (Cu²⁺)?
    1. Green
    2. Pink
    3. Blue
    4. Colorless
  38. When sodium hydroxide is added in drops to a solution containing iron(II) ions (Fe²⁺), what is the color of the resulting precipitate?
    1. Reddish-brown
    2. Dirty green
    3. White
    4. Blue
  39. A student adds aqueous ammonia to an unknown metal salt solution and observes a reddish-brown precipitate that is insoluble in excess. Which cation is likely present?
    1. Fe³⁺
    2. Fe²⁺
    3. Cr³⁺
    4. Al³⁺
  40. What is the characteristic color of aqueous permanganate ions (MnO₄⁻)?
    1. Yellow
    2. Orange
    3. Purple
    4. Colorless
  41. Which of the following anions gives an orange color in an acidic aqueous solution?
    1. Chromate (CrO₄²⁻)
    2. Dichromate (Cr₂O₇²⁻)
    3. Sulfate (SO₄²⁻)
    4. Nitrate (NO₃⁻)
  42. An unknown solution is pale pink. Upon addition of NaOH, a buff (off-white/pale brown) precipitate forms, which darkens on exposure to air. What cation is present?
    1. Co²⁺
    2. Ni²⁺
    3. Mn²⁺
    4. Zn²⁺
  43. What is the typical color of aqueous nickel(II) ions (Ni²⁺)?
    1. Blue
    2. Green
    3. Pink
    4. Yellow
  44. What color precipitate is formed when potassium iodide is added to a solution containing lead(II) ions (Pb²⁺)?
    1. White
    2. Black
    3. Golden yellow
    4. Bright red
  45. Silver ions (Ag⁺) react with halide ions to form precipitates. Which of the following correctly matches the halide to its precipitate color?
    1. Chloride: Yellow
    2. Bromide: Cream
    3. Iodide: White
    4. Fluoride: Black
  46. What color is observed when hydrogen sulfide gas (H₂S) is passed through an acidic solution containing copper(II) ions?
    1. White
    2. Yellow
    3. Brown
    4. Black
  47. An aqueous solution of cobalt(II) chloride (CoCl₂) is typically pink. What color does the precipitate initially appear when a small amount of NaOH is added?
    1. Blue
    2. Green
    3. Yellow
    4. White

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