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Redox Revision

Redox Revision. AS F321 Oct 2012. Definitions. Define the following terms: Reduction Oxidation Disproportionation. Definitions: Answers. Reduction: gain of electrons Oxidation: loss of electrons Disproportionation : the same species is both oxidised and reduced. Oxidation numbers.

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Redox Revision

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  1. Redox Revision AS F321 Oct 2012

  2. Definitions • Define the following terms: • Reduction • Oxidation • Disproportionation

  3. Definitions: Answers • Reduction: gain of electrons • Oxidation: loss of electrons • Disproportionation: the same species is both oxidised and reduced

  4. Oxidation numbers • Work out the oxidation number of the species underlined/highlighted on your card

  5. For each of the following reactions state whether it is a redox reaction or not. If it is a redox reaction state and explain what has been reduced and oxidised. • MgCO3 + H2SO4→ MgSO4 + H2O + CO2 • CuO + C → Cu + CO Extension equation: 3Mn3O4 + 8Al → 9Mn + 4Al2O3

  6. Equation answers • MgCO3 + H2SO4→ MgSO4 + H2O + CO2No change in oxidation state – not a redox reaction (neutralisation) • CuO + C → Cu + CO Redox reaction: Copper reduced as oxidation state changed from +2 to 0. Carbon oxidised as oxidation state changed from 0 to +2. • 3Mn3O4 + 8Al → 9Mn + 4Al2O3Redox reaction: Manganese reduced as oxidation state changed from +2.67 to 0. Aluminium oxidised as oxidation state changed from 0 to +3.

  7. AQA June 11 Qu 5

  8. AQA June 11 Qu 5

  9. Nitric acid is manufactured from ammonia in a process that involves several stages: a) 4NH3(g) + 5O2(g) ↔4NO(g) + 6H2O(g) b) 2NO(g) + O2(g) ↔ 2NO2(g) c) 2NO2(g) + H2O(l) →H+(aq) + NO3–(aq) + HNO2(aq) • For reaction (a) state and explain using oxidation numbers which species have been oxidised and which have been reduced. • For reaction (b) explain what has happened in the reaction in terms of electrons. • Give the oxidation states of nitrogen in each of the species in reaction (c). Explain what type of reaction this is.

  10. Oxygen has been reduced – oxidation state changed from 0 to -2. Nitrogen has been oxidised – oxidation state changed from -3 to +2. • Nitrogen has been oxidised (+2 to +4). It has lost 2 electrons (oxidation is loss of electrons). Oxygen has been reduced (0 to -2). It has gained 2 electrons (reduction is the gain of electrons). • Nitrogen has the following oxidation states in reaction 3: • NO2 = +4 • NO3- = +5 • HNO2 = +3 • This is a disproprtionation reaction as nitrogen has been both oxidised (oxidation number changed from +4 to +5) and reduced (oxidation number changed from +4 to +3)

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