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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. How are electrons transferred?? Observe charges on elements:
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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)
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
Redox Reactions How are electrons transferred?? 2 e- + Cl20 → 2 Cl- Cl2 is REDUCED, since the charge on each Cl is lowered Mg0→ Mg2+ + 2 e- Mg is OXIDIZED, electrons are removed REDuction + OXidation = REDOX
Redox Reactions Reducing Agent: causes reduction (donates electrons) Oxidizing Agent: causes oxidation (accepts electrons) 2 Mg + O2→ 2 MgO Oxidizing Agent = O2 Reducing Agent = Mg
Redox Reactions HALF REACTIONS Mg + Cl2 → MgCl2 Break reaction into two separate (HALF) reactions showing electrons Mg0 → Mg2+ + 2 e- Cl20 + 2 e- → 2 Cl-
Balancing Redox Reactions HALF REACTION METHOD 1. Break reaction into half reactions. 2. Balance each half reaction separately. Use H+ and H2O as needed to balance atoms. 3. Balance charge in each half reaction by adding electrons to one side of the equation.
Balancing Redox Reactions HALF REACTION METHOD 4. Obtain equal number of electrons in each half reaction by multiplying entire equation by a constant. 5. Add the 2 half reactions back together so that the electrons cancel. 6. Convert from acidic to basic (if necessary). Add enough OH- to each side to cancel H+ by converting to H2O.
Balancing Redox Reactions • Balance the following for acidic and basic solution: • ClO–(aq) + Cr(OH)4–(aq) CrO42–(aq) + Cl–(aq) • NO3–(aq) + Cu(s) NO(g) + Cu2+(aq) • MnO4–(aq) + IO3–(aq) MnO2(s) + IO4–(aq)