Transition Metals

• Which two elements have exceptional electron configurations due to stability considerations?

  Cr and Cu
• A transition metal is defined as a metal that forms stable ions with a complete d sub-shell.

  False
• What are the four characteristic properties of transition metals?

  Complex formation, catalytic activity, variable oxidation states, formation of colored ions
• A complex is defined as a central metal ion surrounded by ligands
• The coordination number of a complex ion is always equal to the number of ligands attached.

  False
• What is the coordination number of the complex ion [Fe(CN)₆]³⁻?

  6
• Two common shapes of complex ions are octahedral and tetrahedral.
• Complexes with water or ammonia ligands generally have an octahedral shape.
• What is the shape of the complex ion [CuCl₄]²⁻?

  Tetrahedral
• Both the 3d and 4s electrons in transition metals can be involved in bonding because they are close in energy.
• What is the oxidation state of manganese in MnO₂?

  +4
• What is the oxidation state of vanadium in V₂O₅?

  +5
• The oxidation state of manganese in MnO₄⁻ is +7
• Order the common oxidation states of vanadium from highest to lowest.

  1️⃣ +5

  2️⃣ +4

  3️⃣ +3

  4️⃣ +2
• What color is a solution containing VO²⁺ ions?

  Blue
• Zinc reduces VO₂⁺ to VO²⁺ in acidic conditions.
• Which species in the electrode potential table is the strongest oxidising agent?

  O₂(g)
• Zinc can reduce VO₂⁺ to V²⁺ but not further because the redox potential of V²⁺/V is lower
• What is observed when an aldehyde reacts with Tollens' reagent?

  Silver mirror
• Ketones react with Tollens' reagent.

  False
• What does the redox potential measure?

  Ease of reduction
• How does changing the ligand affect the redox potential of a metal ion?

  Changes its value
• What is the color change at the end point in a redox titration using potassium manganate(VII)?

  Colorless to pale pink
• What is the half-equation for the oxidation of hydrogen peroxide?

  H₂O2(aq) → O₂(g) + 2H+(aq) + 2e-
• What is the overall balanced equation for the reaction between ethanedioate ions and manganate(VII) ions?

  5C₂O4² + 2MnO4 + 16H+ → 10 CO₂ + 2Mn²+ + 8H₂O
• Hydrated iron(II) ethanedioate can be analysed by titration using potassium manganate(VII) in acidic solution
• What is the overall balanced equation for the reaction between iron(II) ethanedioate and manganate(VII) ions?

  3MnO4 + 24H+ + 5Fe²+ + 5C₂O4²- → 5Fe³+ + 10CO₂ + 3Mn²+ + 12H₂O
• A catalyst increases the rate of a chemical reaction without being changed in chemical composition or amount
• A catalyst lowers the activation energy of a reaction.
• What happens to ΔH in the presence of a catalyst?

  ΔH remains unchanged
• A heterogeneous catalyst is in a different state or phase from the reactants.
• Increasing the surface area of a heterogeneous catalyst increases the reaction rate.
• Impurities in reactants may bind to active sites on the catalyst surface, causing it to become poisoned.
• Steps involved in the mechanism of the Contact Process using vanadium(V) oxide as a catalyst:

  1️⃣ Sulfur dioxide diffuses onto active sites

  2️⃣ Vanadium(V) oxide oxidises sulfur dioxide

  3️⃣ Vanadium(IV) oxide reacts with oxygen

  4️⃣ Vanadium(V) oxide is regenerated
• A homogeneous catalyst is in the same phase as the reactants.
• The intermediate species in the iron(II)-catalyzed reaction between peroxodisulfate and iodide ions is Fe³⁺.
• Arrange the electrode potentials in descending order:

  1️⃣ S₂O₈²⁻ / SO₄²⁻

  2️⃣ Fe³⁺ / Fe²⁺

  3️⃣ I₂ / I⁻
• An autocatalyst is a reaction product that acts as a catalyst.
• The intermediate species in the autocatalytic reaction between manganate(VII) and ethanedioate ions is Mn³⁺.