OCR A- Level Chemistry Paper 1
Questions & Answers
Define Transition element - ANSWERSA d-block element that can form at least one
stable ion with an incomplete d sub-shell
Why aren't scandium and Zinc transition elements? - ANSWERSCannot 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 - ANSWERSMnO4 -
(purple)
MnO4 2- (green)
Mn 2+ (pale pink)
Name the oxidation state and coloured ions for Titanium - ANSWERSTi 3+ (purple)
Ti 2+ (violet)
Name the oxidation state and coloured ions for Vanadium - ANSWERSVO2 + (yellow)
VO 2+ (blue)
V 3+ (green)
V 2+ (violet)
Name the oxidation state and coloured ions for Chromium - ANSWERSCr2O7 2-
(orange)
Cr 3+ (violet)
Name the oxidation state and coloured ions for Iron - ANSWERSFe 3+ (yellow)
Fe 2+ (pale green)
Name the oxidation state and coloured ions for Cobalt - ANSWERSCo 2+ (pink)
Name the oxidation state and coloured ions for Nickel - ANSWERSNi 2+ (green)
, Name the oxidation state and coloured ions for Copper - ANSWERSCu 2+ (pale blue)
Why are transition elements good catalysts? (+ one downside) - ANSWERSCan 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)? - ANSWERSA coloured hydroxide
precipiate is formed and takes the form of [M(H2O6)] n+.
Equation and colour of hydroxide precipitate for Copper (II) - ANSWERSPale 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) - ANSWERSPale 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) - ANSWERSYellow solution to
orange precipitate that darkens
[Fe(H2O)6]3+ + 3OH- --> [Fe(OH)3(H2O)3] 3H2O
[Fe(H2O)6]3+ + NH3 --> [Fe(OH)3(H2O)3] + 3NH4+
Equation and colour of hydroxide precipitate for Manganese (II) - ANSWERSPale pink
solution to pink / buff precipitate that darkens
[Mn(H2O)6]2+ + 2OH- --> [Mn(OH)2(H2O)4] + 2H2O
[Mn(H2O)6]2+ + 2NH3 --> [Mn(OH)2(H2O)4] + 2NH4+
Equation and colour of hydroxide precipitate for Chromium (III) - ANSWERSGreen
solution to grey / green precipitate
[Cr(H2O)6]3+ + 3OH- --> [Cr(OH)3(H2O)3] + 3H2O
[Cr(H2O)63+ + 3NH3 --. [Cr(OH)3(H2O)3 + 3 NH4 +
Define complex ion - ANSWERSA metal ion surrounded by coordinately bonded
ligands.
Questions & Answers
Define Transition element - ANSWERSA d-block element that can form at least one
stable ion with an incomplete d sub-shell
Why aren't scandium and Zinc transition elements? - ANSWERSCannot 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 - ANSWERSMnO4 -
(purple)
MnO4 2- (green)
Mn 2+ (pale pink)
Name the oxidation state and coloured ions for Titanium - ANSWERSTi 3+ (purple)
Ti 2+ (violet)
Name the oxidation state and coloured ions for Vanadium - ANSWERSVO2 + (yellow)
VO 2+ (blue)
V 3+ (green)
V 2+ (violet)
Name the oxidation state and coloured ions for Chromium - ANSWERSCr2O7 2-
(orange)
Cr 3+ (violet)
Name the oxidation state and coloured ions for Iron - ANSWERSFe 3+ (yellow)
Fe 2+ (pale green)
Name the oxidation state and coloured ions for Cobalt - ANSWERSCo 2+ (pink)
Name the oxidation state and coloured ions for Nickel - ANSWERSNi 2+ (green)
, Name the oxidation state and coloured ions for Copper - ANSWERSCu 2+ (pale blue)
Why are transition elements good catalysts? (+ one downside) - ANSWERSCan 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)? - ANSWERSA coloured hydroxide
precipiate is formed and takes the form of [M(H2O6)] n+.
Equation and colour of hydroxide precipitate for Copper (II) - ANSWERSPale 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) - ANSWERSPale 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) - ANSWERSYellow solution to
orange precipitate that darkens
[Fe(H2O)6]3+ + 3OH- --> [Fe(OH)3(H2O)3] 3H2O
[Fe(H2O)6]3+ + NH3 --> [Fe(OH)3(H2O)3] + 3NH4+
Equation and colour of hydroxide precipitate for Manganese (II) - ANSWERSPale pink
solution to pink / buff precipitate that darkens
[Mn(H2O)6]2+ + 2OH- --> [Mn(OH)2(H2O)4] + 2H2O
[Mn(H2O)6]2+ + 2NH3 --> [Mn(OH)2(H2O)4] + 2NH4+
Equation and colour of hydroxide precipitate for Chromium (III) - ANSWERSGreen
solution to grey / green precipitate
[Cr(H2O)6]3+ + 3OH- --> [Cr(OH)3(H2O)3] + 3H2O
[Cr(H2O)63+ + 3NH3 --. [Cr(OH)3(H2O)3 + 3 NH4 +
Define complex ion - ANSWERSA metal ion surrounded by coordinately bonded
ligands.
