Physical chemistry

• Reduction potentials and volts of some half cells

  • A2+(aq) + 2e- → A(s) (-2.80V)
  • B+(aq) + e- → B(s) (-1.50V)
  • 2C+(aq) + 2e- → C2(g) (0.00V)
  • D2(g) + 2e- → 2D-(aq) (+3.20V)
  • G+(aq) + e- → G(s) (+1.80V)
• Oxidizing power


  The ability of a species to oxidize other substances
• Reducing power


  The ability of a species to reduce other substances
• Calculating electrode potential (e.m.f) for a cell

  Using half-cells of A and B
• Oxidation number


  The charge on an atom in a compound
• Chromium in Cr2O72- has an oxidation number of +6
• Phosphorus in PO43- has an oxidation number of +5
• Determining charge on an ion of element P


  Using current, time, and mass deposited
• Calculating EMF of a dry cell

  Using reduction potentials of Zn and NH4+/NH3
• Reactions between metals and solutions containing ions

  • Cu with Zn2+, Zn with Ag+, Mg with Cu2+, Ag with Mg2+
• Ionic equation for a reaction that occurred
• Fluorine cannot be obtained by electrolysis of KF in water
• Reaction of sodium thiosulfate and dilute hydrochloric acid

  Na2S2O3 + 2HCl → SO2 + S + 2NaCl + H2O
• Use of reaction in (b) above in school laboratory

  To test for the presence of sulfur dioxide
• Writing cell notation for combination of half-cells that would give the highest EMF

  Mg|Mg2+||Cl-|Cl2
• Reactions between metals and solutions containing ions


  • Cu with Zn2+, Zn with Ag+, Ag with Pb2+
• Metals in order of reactivity

  • Ag, Cu, Zn
• Adding hydrochloric acid to Cr2O72-/Cr3+ equilibrium

  Shifts equilibrium to the right, increasing [Cr3+]
• Calculating mass of product at electrode T


  Using current, time, and Faraday's constant
• Calculating standard reduction potential of B

  Using given reduction potentials
• Calculating time to deposit 2.39g of copper during electrolysis


  Using current, mass, and Faraday's constant
• Strongest reducing agent


  U, because it has the most negative reduction potential
• Determining the two half-cells that would produce the highest EMF


  U and Z, EMF = 3.15V
• Elements represented by letters

  • U
  • V
  • W
  • X
  • Z
• Standard electrode potentials


  Measure of the tendency of an element to lose or gain electrons
• Strongest reducing agent


  • Has the most negative standard electrode potential
• Determining the strongest reducing agent

  1. Compare the standard electrode potentials

  2. The element with the most negative potential is the strongest reducing agent
• Highest EMF


  Produced by the half-cell pair with the largest difference in standard electrode potentials
• Element X represents the standard electrode potential of 0.00 volts
• Reaction at metal Z electrode

  1. Oxidation of Z to Z ions

  2. Releasing electrons
• Reaction at metal V electrode

  1. Reduction of V ions to V metal

  2. Accepting electrons
• Cell representation


  Indicates the arrangement of the half-cells and the direction of electron flow
• EMF of electrochemical cell

  Difference in standard electrode potentials between the two half-cells
• Overall cell reaction


  Combination of the half-reactions at the two electrodes
• Uses of electrochemical cells

  • Batteries
  • Electroplating
  • Electrolysis
• Salt bridge


  Allows the flow of ions between the half-cells to complete the circuit
• Salts used in salt bridge

  • Potassium chloride
  • Sodium nitrate
• Strongest reducing agent


  Element with the most negative standard electrode potential
• Strongest oxidizing agent


  Element with the most positive standard electrode potential
• Determining EMF of electrochemical cell

  Difference in standard electrode potentials between the two half-cells