CHEMISTRY 7405 PAPER 3 PRACTICE TEST
2026 QUESTION BANK AND CORRECT
ANSWERS REVIEW
◉ Why aren't scandium and Zinc transition elements. Answer:
Cannot form stable ions with an incomplete d-sub shell. Sc 3+ has an
empty d-sub shell and Zn 2+ has a full d sub shell.
◉ Name the oxidation states and coloured ions for Manganese.
Answer: MnO4 - (purple)
MnO4 2- (green)
Mn 2+ (pale pink)
◉ Name the oxidation state and coloured ions for Titanium. Answer:
Ti 3+ (purple)
Ti 2+ (violet)
◉ Name the oxidation state and coloured ions for Vanadium.
Answer: VO2 + (yellow)
VO 2+ (blue)
V 3+ (green)
V 2+ (violet)
,◉ Name the oxidation state and coloured ions for Chromium.
Answer: Cr2O7 2- (orange)
Cr 3+ (violet)
◉ Name the oxidation state and coloured ions for Iron. Answer: Fe
3+ (yellow)
Fe 2+ (pale green)
◉ Name the oxidation state and coloured ions for Cobalt. Answer: Co
2+ (pink)
◉ Name the oxidation state and coloured ions for Nickel. Answer: Ni
2+ (green)
◉ Name the oxidation state and coloured ions for Copper. Answer:
Cu 2+ (pale blue)
◉ Why are transition elements good catalysts? (+ one downside).
Answer: Can easily change oxidation states by gaining or loosing
electrons within the d-orbital. Transition metals are also good at
adsorbing substances onto their surfaces lower than the activation
energy of the reactions. Good for industry and environment as
reactions can happen faster at lower temperatures and pressure.
, Poses health risks with exposure as many metals and their
compounds are toxic.
◉ What happens when an aqueous solution of a tranisition element
ions is mixed with sodium hydroxide (NaOH) or ammonia (NH3)?.
Answer: A coloured hydroxide precipiate is formed and takes the
form of [M(H2O6)] n+.
◉ Equation and colour of hydroxide precipitate for Copper (II).
Answer: Pale blue solution to blue precipitate
[Cu(H2O6)]2+ + 2OH- --> [Cu(OH)2(H2O)4] + 2H2O
[Cu(H2O)6]2+ + 2NH3 --> [Cu(OH)2(H2O)4] + 2NH4+
◉ Equation and colour of hydroxide precipitate for Iron (II). Answer:
Pale green solution to green precipitate that darkens
[Fe(H2O)6]2+ + 2OH- --> [Fe)OH)2(H2O)4] + 2H2O
[Fe(H2O)6]2+ + 2NH3 --> [Fe(OH)2(H2O)4] + 2NH4+
◉ Equation and colour of hydroxide precipitate for Iron (III).
Answer: Yellow solution to orange precipitate that darkens
[Fe(H2O)6]3+ + 3OH- --> [Fe(OH)3(H2O)3] 3H2O
2026 QUESTION BANK AND CORRECT
ANSWERS REVIEW
◉ Why aren't scandium and Zinc transition elements. Answer:
Cannot form stable ions with an incomplete d-sub shell. Sc 3+ has an
empty d-sub shell and Zn 2+ has a full d sub shell.
◉ Name the oxidation states and coloured ions for Manganese.
Answer: MnO4 - (purple)
MnO4 2- (green)
Mn 2+ (pale pink)
◉ Name the oxidation state and coloured ions for Titanium. Answer:
Ti 3+ (purple)
Ti 2+ (violet)
◉ Name the oxidation state and coloured ions for Vanadium.
Answer: VO2 + (yellow)
VO 2+ (blue)
V 3+ (green)
V 2+ (violet)
,◉ Name the oxidation state and coloured ions for Chromium.
Answer: Cr2O7 2- (orange)
Cr 3+ (violet)
◉ Name the oxidation state and coloured ions for Iron. Answer: Fe
3+ (yellow)
Fe 2+ (pale green)
◉ Name the oxidation state and coloured ions for Cobalt. Answer: Co
2+ (pink)
◉ Name the oxidation state and coloured ions for Nickel. Answer: Ni
2+ (green)
◉ Name the oxidation state and coloured ions for Copper. Answer:
Cu 2+ (pale blue)
◉ Why are transition elements good catalysts? (+ one downside).
Answer: Can easily change oxidation states by gaining or loosing
electrons within the d-orbital. Transition metals are also good at
adsorbing substances onto their surfaces lower than the activation
energy of the reactions. Good for industry and environment as
reactions can happen faster at lower temperatures and pressure.
, Poses health risks with exposure as many metals and their
compounds are toxic.
◉ What happens when an aqueous solution of a tranisition element
ions is mixed with sodium hydroxide (NaOH) or ammonia (NH3)?.
Answer: A coloured hydroxide precipiate is formed and takes the
form of [M(H2O6)] n+.
◉ Equation and colour of hydroxide precipitate for Copper (II).
Answer: Pale blue solution to blue precipitate
[Cu(H2O6)]2+ + 2OH- --> [Cu(OH)2(H2O)4] + 2H2O
[Cu(H2O)6]2+ + 2NH3 --> [Cu(OH)2(H2O)4] + 2NH4+
◉ Equation and colour of hydroxide precipitate for Iron (II). Answer:
Pale green solution to green precipitate that darkens
[Fe(H2O)6]2+ + 2OH- --> [Fe)OH)2(H2O)4] + 2H2O
[Fe(H2O)6]2+ + 2NH3 --> [Fe(OH)2(H2O)4] + 2NH4+
◉ Equation and colour of hydroxide precipitate for Iron (III).
Answer: Yellow solution to orange precipitate that darkens
[Fe(H2O)6]3+ + 3OH- --> [Fe(OH)3(H2O)3] 3H2O
