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Types of Chemical Reactions

Types of Chemical Reactions. Oxidation–Reduction (Redox) Reaction: A reaction in which one or more electrons are transferred between reaction partners. Mg (s) + Cl 2 ( g )  MgCl 2 ( s ). Redox Reactions. Electrolyte: a solution that conducts electricity - or –

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Types of Chemical Reactions

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  1. Types of Chemical Reactions • Oxidation–Reduction (Redox) Reaction:A reaction in which one or more electrons are transferred between reaction partners. Mg (s) + Cl2 (g) MgCl2(s)

  2. Redox Reactions Electrolyte: a solution that conducts electricity - or – An ionic compound dissolved in water

  3. Redox Reactions Strong electrolyte: almost all molecules are ionized. HCl, HNO3, NaCl Weak electrolyte: only a small proportion of the ions are formed. H2SO3, HC2H3O2

  4. Electrolytes in Solution • Why do ionic compounds conduct electricity when molecular ones generally do not?

  5. Electrolytes in Solution • Electrolytes:Dissolve in water to produce ionic solutions. • Nonelectrolytes: Do not form ions when they dissolve in water.

  6. Electrolytes in Solution • Dissociation: • The process by which a compound splits up to form ions in the solution.

  7. Redox Reactions How are electrons transferred?? Observe charges on elements: Mg0 (s) + Cl20(g) MgCl2(s) Mg0 (s) + Cl20(g) Mg2+ + 2Cl- Mg0→ Mg2+ + 2 e- 2 e- + Cl20 → 2 Cl- So electrons are TRANSFERRED from Mg to Cl2

  8. Redox Reactions Electrochemical Series: A table showing the relative oxidizing strengths of different species. Helps to predict the outcome of unknown redox reactions Zn + Cu2+ → ?? Check Table…

  9. Activity Series of Elements

  10. Redox Reactions Zn + Cu2+ → ?? From Table: Zn is a stronger reducing agent than Cu. Therefore the electrons are more likely to reside with Cu in the product: Zn + Cu2+ → Zn2+ + Cu

  11. Redox Reactions OXIDATION NUMBER Effective charge on any atom NaCl: Na +1, Cl -1 MgCl2: Mg +2, Cl -1 H2O: H +1, O -2 MgO: Mg +2, O -2

  12. Redox Reactions CALCULATING OXIDATION NUMBER 1. The sum of the O.N.s of all of the atoms in a molecule or ion is equal to its total charge. NaCl: ONNa + ONCl = 0 +1 + (-1) = 0 SO42-: ONS + 4 x ONO = -2 6 + 4x(-2) = -2

  13. Redox Reactions CALCULATING OXIDATION NUMBER 2. For atoms in the elemental form the oxidation number is zero. Mg (s): ON = 0 O2 (g): ON = 0

  14. Redox Reactions CALCULATING OXIDATION NUMBER 3. Remember some common oxidation numbers: Group 1 → +1 Group 2 → +2 Halogens → -1 Oxygen → -2 Hydrogen → +1, -1

  15. Redox Reactions CALCULATING OXIDATION NUMBER HSO3- ONS = ?? ONH + ONS + 3(ONO) = -1 ONH = +1, ONO = -2 So ONs = -1 – (1) – (3 x (-2)) = +4

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