8.3. Homogeneous and heterogeneous catalysts
A subsection of Chemistry, 9701, through 8. Reaction kinetics
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Define transition element. Sketch the shape of a 3dz2 orbital. z x y  Manganese(oxide, MnO2, acts as a heterogeneous catalyst in the decomposition of hydrogenperoxide, H2O2. Explain what is meant by a heterogeneous catalyst. Describe the mode of action of a heterogeneous catalyst in a reaction. Manganese(oxide, Mn2O7, can be made by treatment of KMnO4 with concentrated sulfuricacid (reaction 1). Mn2O7 readily decomposes at room temperature to form manganese(oxide and a colourless diatomic gas (reaction 2). Construct equations for both the reactions described. reaction 1 reaction 2  Aqueous manganese(ions show similar chemical properties to aqueous copper(ions when reacted separately with NaOHand with concentrated HCl. Write the ionic equation, and state the type of reaction, for the reaction of [Mn(H2O)6]2+ with NaOH. ionic equation type of reaction  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  Table2.1 lists relevant electrode potentials for some electrode reactions. Table 2.1 electrode reaction E o / V Mn2+ + 2e– Mn –1.18 Cl 2 + 2e– 2Cl – +1.36 2HOCl + 2H+ + 2e– Cl 2 + 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+reacts with Cl 2. State the type of reaction. formula of manganese species formed type of reaction  
9701_s22_qp_41
THEORY
2022
Paper 4, Variant 1
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Define transition element. Sketch the shape of a 3dz2 orbital. z x y  Manganese(oxide, MnO2, acts as a heterogeneous catalyst in the decomposition of hydrogenperoxide, H2O2. Explain what is meant by a heterogeneous catalyst. Describe the mode of action of a heterogeneous catalyst in a reaction. Manganese(oxide, Mn2O7, can be made by treatment of KMnO4 with concentrated sulfuricacid (reaction 1). Mn2O7 readily decomposes at room temperature to form manganese(oxide and a colourless diatomic gas (reaction 2). Construct equations for both the reactions described. reaction 1 reaction 2  Aqueous manganese(ions show similar chemical properties to aqueous copper(ions when reacted separately with NaOHand with concentrated HCl. Write the ionic equation, and state the type of reaction, for the reaction of [Mn(H2O)6]2+ with NaOH. ionic equation type of reaction  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  Table2.1 lists relevant electrode potentials for some electrode reactions. Table 2.1 electrode reaction E o / V Mn2+ + 2e– Mn –1.18 Cl 2 + 2e– 2Cl – +1.36 2HOCl + 2H+ + 2e– Cl 2 + 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+reacts with Cl 2. State the type of reaction. formula of manganese species formed type of reaction  
9701_s22_qp_43
THEORY
2022
Paper 4, Variant 3
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Catalysts can be described as homogeneous or heterogeneous. What is meant by the terms homogeneous and heterogeneous? By using iron and its compounds as examples, outline the different modes of action of homogeneous and heterogeneous catalysis. Choose one example of each type, and for each example you should ● state what the catalyst is, and whether it is acting as a homogeneous or a heterogeneous catalyst, ● write a balanced equation for the reaction, ● outline how the catalyst you have chosen works to decrease the activation energy. The reaction between SO2, NO2 and O2 occurs in two steps. NO2 + SO2 → NO + SO3 ∆H 1 = –88 kJ mol–1 NO + 2 1O2 → NO2 ∆H 2 = –57 kJ mol–1 The activation energy of the fi rst reaction, Ea1, is higher than that of the second reaction, Ea2. Use the axes below to construct a fully-labelled reaction pathway diagram for this reaction, labelling Ea1, Ea2, ∆H 1 and ∆H 2. energy extent of reaction NO2 + SO2 o o o o
9701_w12_qp_41
THEORY
2012
Paper 4, Variant 1
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Catalysts can be described as homogeneous or heterogeneous. What is meant by the terms homogeneous and heterogeneous? By using iron and its compounds as examples, outline the different modes of action of homogeneous and heterogeneous catalysis. Choose one example of each type, and for each example you should ● state what the catalyst is, and whether it is acting as a homogeneous or a heterogeneous catalyst, ● write a balanced equation for the reaction, ● outline how the catalyst you have chosen works to decrease the activation energy. The reaction between SO2, NO2 and O2 occurs in two steps. NO2 + SO2 → NO + SO3 ∆H 1 = –88 kJ mol–1 NO + 2 1O2 → NO2 ∆H 2 = –57 kJ mol–1 The activation energy of the fi rst reaction, Ea1, is higher than that of the second reaction, Ea2. Use the axes below to construct a fully-labelled reaction pathway diagram for this reaction, labelling Ea1, Ea2, ∆H 1 and ∆H 2. energy extent of reaction NO2 + SO2 o o o o
9701_w12_qp_42
THEORY
2012
Paper 4, Variant 2
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Questions Discovered
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