Unit 13, Ch. 22

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Unit 13, Ch. 22 Redox Reactions
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Vocab -
Reduction Gain of e- Loss of oxygen
Oxidation Loss of e- Gain of oxygen
Oxidation Is Losing e- Reduction Is Gaining
e-

• Oxidation reduction reaction Any chemical
  change in which one compound is oxidized (loses
  electrons) and another compound is reduced (gains
  electrons) also called a redox reaction.

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• Mg S ? Mg2 S2-

Loses e-s magnesium atom is said to be oxidized
to a magnesium ion Sulfur atom gains two e-s and
is reduced to a sulfide ion
Oxidation Mg ? Mg2 2e- (loss of
electrons) Reduction S 2e- ? S2- (gain
of electrons)
Half- Reactions shows either reduction or
oxidation, but not both. Only the species of atom
that is involved in the change
Sample Prob 22-1 remember that individual atoms
and compounds are neutral (have no
charge) 2AgNO3(aq) Cu(s) ? Cu(NO3)2(aq)
2Ag(s)
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Practice Assigning Oxidation s

• Use the oxidation numbers to identify which atoms
  are oxidized and which are reduced in each
  reaction.
• a. Cl2(g) 2HBr(aq) ? 2HCl(aq) Br2(l)
• b. C(s) O2(g) ? CO2(g)
• c. Zn(s) 2MnO2(s) 2NH4Cl(aq) ?
  ZnCl2(aq) Mn2O3(s) 2NH3(g) H2O(l)

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• - The substance that is oxidized is called the
  reducing agent.
• - The substance that is reduced is called the
  oxidizing agent.
• - Single replacement and combustion reactions are
  redox reactions, double replacement is not a
  redox reaction.

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• Electrochemistry The branch of chemistry that is
  the study of the relationship between electric
  forces and chemical reactions.
• Voltage The potential difference or
  electromotive force, measured in volts it
  represents the amount of work that moving an
  electric charge between two points would take.
• Electrode A conductor used to establish
  electrical contact with a nonmetallic part of a
  circuit, such as an electrolyte.
• electrochemical cell A system that contains two
  electrodes separated by an electrolyte phase.
• Cathode The electrode on whose surface reduction
  takes place.
• Anode The electrode on whose surface oxidation
  takes place anions migrate toward the anode, and
  electrons leave the system from the anode.