Manganese(IV) oxide, MnO2, acts as a heterogeneous catalyst in the decomposition of hydrogen peroxide, H2O2.

1. (a)Define transition element.[1]
2. (b)Sketch the shape of a 3d₂² orbital. Z y X[1]
3. (c)(i)Explain what is meant by a heterogeneous catalyst.[1]
4. (c)(ii)Describe the mode of action of a heterogeneous catalyst in a reaction.[3]
5. (d)Manganese(VII) oxide, Mn₂O₇, can be made by treatment of KMnO₄ with concentrated sulfuric acid (reaction 1). Mn₂O₇ readily decomposes at room temperature to form manganese(IV) oxide and a colourless diatomic gas (reaction 2). Construct equations for both the reactions described. reaction 1 reaction 2[2]
6. (e)(i)Aqueous manganese(II) ions show similar chemical properties to aqueous copper(II) ions when reacted separately with NaOH(aq) and with concentrated HCl. Write the ionic equation, and state the type of reaction, for the reaction of [Mn(H2O)6]2+ with NaOH(aq). ionic equation type of reaction[2]
7. (e)(ii)Write the ionic equation, and state the type of reaction, for the reaction of [Mn(H2O)6]2+ with concentrated HCl. ionic equation type of reaction[2]
8. (e)(iii)Table 2.1 lists relevant electrode potentials for some electrode reactions. Table 2.1 electrode reaction E°/V Mn2+ + 2e- ⇌ Mn -1.18 Cl2 + 2e¯ ⇌ 2Cl- +1.36 2HOCl + 2H+ + 2e¯ ⇌ Cl₂ + 2H2O +1.64 MnO2 + 4H+ + 2e¯ = Mn2+ + 2H2O +1.23 MnO4 + 4H+ + 3e¯ MnO2 + 2H2O +1.67 Suggest the formula of the manganese species formed when Mn2+(aq) reacts with Cl2. State the type of reaction. formula of manganese species formed type of reaction[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.