I- Transition Metals =) Flashcards
Fe2+ ions catalyse the reaction between peroxodisulfate(VI) ions and iodide ions in aqueous solution.
S2O8 2–(aq) + 2 I– (aq) → 2 SO4 2– (aq) + I2(aq)
Explain why this reaction is slow before the catalyst is added. (2)
- 2 -ve ions repel
- high Ea
S2O8 2–(aq) + 2 I– (aq) → 2 SO4 2– (aq) + I2(aq)
Give a reason why Zn2+ ions do not catalyse this reaction. (1)
Zn ions only have 1 oxidation state
Explain why an aqueous solution containing [Fe(H2O)6]
3+ ions has a lower pH than an aqueous solution containing [Fe(H2O)6]
2+ ions. (3)
- Fe3+ = smaller/ ↑ charge density
- ↑ polarising
- ∴ ↑ O-H bonds in H2O ligands break –> release ↑ H+
Give the overall ionic equation for the oxidation of Fe2+ by manganate(VII) ions, in acidic conditions. (1)
5Fe2+ + MnO4– + 8H+ –> 5Fe3+ + Mn2+ + 4H2O
Titration between Fe2+ and excess sulfuric acid, with potassium mangante (VII) solution.
State the colour change at the end point of the titration. (1)
colourless –> pink
Suggest why the colour change is colourless to pink at the end of a titration using KMnO4. (1)
just after end point, MnO4- in XS
Explain why colorimetry cannot be used to determine the concentration of solutions containing [CuCl2]-.
In your answer refer to the electron configuration of the metal ion. (2)
- 3d10- full 3d orbital
- colourless
Explain the meaning of the term autocatalyst. (1)
product of reaction catalyses the reaction
2 MnO4– + 5 C2O42– + 16 H+ → 2 Mn2+ + 10 CO2 + 8 H2O
The mixture is warmed before the addition of potassium manganate(VII) solution because the reaction is slow at first. When more potassium manganate(VII) solution is added, the mixture goes colourless quickly due to the presence of an autocatalyst.
Explain, using equations where appropriate, why the reaction is slow at first and then goes quickly. (3)
- -ve ions repel
- high Ea
- attraction betw opp. charged ions (-ve reactants w/ +ev catalyst)
What is observed when concentrated hydrochloric acid is added to an aqueous
solution of CuSO4 until no further change occurs?
[1 mark]
A A colourless gas is evolved and a precipitate forms.
B A colourless gas is evolved and no precipitate forms.
C A precipitate forms that dissolves in an excess of
concentrated hydrochloric acid.
D The solution changes colour and no precipitate forms.
D
What forms when a solution of sodium carbonate is added to a solution of gallium(III) nitrate? [1 mark]
A. A white precipitate of gallium(III) carbonate.
B. A white precipitate of gallium(III) hydroxide.
C. A white precipitate of gallium(III) carbonate and
bubbles of carbon dioxide.
D. A white precipitate of gallium(III) hydroxide and
bubbles of carbon dioxide.
D
When anhydrous aluminium chloride reacts with water, solution Y is formed that contains a complex aluminium ion, Z, and chloride ions.
Give an equation for this reaction.
(1)
AlCl3 + 6H2O –> [Al(H2O)6]3+ + 3Cl-
[Fe(H2O)6]3+ —> [Fe(H2O)6]2+
Suggest a reagent for the reaction. (1)
XS Zn
In the Contact process, sulfur(IV) oxide is converted into sulfur(VI) oxide using vanadium(V) oxide as a catalyst.
Give two equations to show how the vanadium(V) oxide acts as a catalyst in this process. (2)
1️⃣ SO2 + V2O5 –> SO3 + V2O4
2️⃣ V2O4 + 1/2 O2 –> V2O5
Copper (I) iodide is a white solid.
Explain why it is white. (2)
- Full 3d subshell
- x d-d transitions possible/ cannot absorb visible light
