Lecture 1: Electrochemical and Electrolytic Cells

Zn(cs)+Cu2+Z_{n(cs)}+ {C_{u}}^{2+} (aq)Zn2+_{(aq)}\rightarrow {Z_{n}}^{2+} (aq)+Cu(s)_{(aq)}+ {C_{u(s)}} (Cu(s){C_{u(s)}} - Reduced from Cu2+{C_{u}}^{2+} (aq)_{(aq)} )

Zn(s)2n2++2eZ_{n(s)}\rightarrow {2_{n}}^{2+}+2e^{-} (2n2+{2_{n}}^{2+} oxidized from Zn(s)Z_{n(s)} )

Cu2+{C_{u}}^{2+} (aq)+2eCu(s)_{(aq)}+2e^{-}\rightarrow C_{u(s)}

\rightarrow Movement of Cations

\leftarrow Movement of anions

Flow of Electrons

At some point it will stop producing electric current

  • When all Cu2+{C_{u}}^{2+} ions are deposited
  • When all Zn2+{Z_{n}}^{2+} are gone

But even before all the Zn2+{Z_{n}}^{2+} ions are gone electric current stops


Build up of Zn2+{Z_{n}}^{2+} excess . (Positive Ion)

15Zn2+15 {Z_{n}}^{2+}

20NO320 {NO_{3}}^{-}


Excess Negative Ion

5Cu2+5 {C_{u}}^{2+}

20NO320 {NO_{3}}^{-}


Electrochemical cell - Produces electricity

  • Stops producing electric current because one has a build up of + ion and the other - ion \rightarrow they don't want to give other charge up.

Salt Bridge - Overt the charge build up negative/positive charged ions.

Electrolytic Cell - Produce chemical change by an electric current by passing electricity.


Na++eNa{N_{a}}^{+}+e^{-}\rightarrow N_{a}

2CICI2+2e2CI^{-}\rightarrow CI_{2}+2e^{-}

NaCIN_{a}CI - Producing electric current from chemical change


Cathode - (-) charge Rod

Anode - (+) charge Rod

  • Given by the process, not the charge.


Cathode - If reduction occurs

Anode - If oxidation occurs

  • Accepted - left electron is Anode


Cathode - Gains weight (metal is deposited)

Anode - Loses weight (Goes to the solution)


Rods in electrolytic cells

  • Non-spontaneous redox reactions can be made to occur in an elctrolytic cell by the addition of electrical energy.

Definition for Electrolytic Cell and Electrochemical Energy

  • Electrochemical change by electric current
  • Electric current from chemical change.


Zn(s)+Cu2+Z_{n(s)}+{C_{u}}^{2+} (aq)_{(aq)} Zn2+\rightarrow {Z_{n}}^{2+} (aq)+Cu(s) _{(aq)}+C_{u(s)}

Cu(s)C_{u(s)} reduced from Cu2+{C_{u}}^{2+} (aq)_{(aq)}

Zn2+{Z_{n}}^{2+} (aq) _{(aq)} oxidated from Zn(s)Z_{n(s)}

Zn(s)Z_{n(s)} Zn2+\rightarrow {Z_{n}}^{2+} +2e+2e^{-} Cu2+{C_{u}}^{2+} (aq)_{(aq)} +2e+2e^{-} \rightarrowCu(s)C_{u(s)}

\rightarrow Movement of Cations

\leftarrow Movement of Anions


Oxidation - 2I2I^{-} (aq)_{(aq)} \rightarrow I2(s)+2eI_{2(s)}+2e^{-}

Reduction - MnO4M_{n}{O_{4}}^{-} (aq)+8M+_{(aq)}+8M^{+} (aq)+5eMn2+_{(aq)}+5e^{-}\rightarrow {M_{n}}^{2+} (aq)+4M2O(1)_{(aq)}+4M_{2}O_{(1)}

Copper electrodes don't react

They are just for the electric contact. (conductor)

2MnO42M_{n}{O_{4}}^{-} (aq)+16M+_{(aq)}+16M^{+} (aq)10I_{(aq)}10 I^{-} (aq)_{(aq)} 2Mn2+\rightarrow {2M_{n}}^{2+} (aq)+5I2(s)_{(aq)} + 5 I_{2(s)} +8H2O1+8H_{2}O_{1}


When writing full reaction:

  1. ee^{-} on opposite sides
  2. Left \rightarrow Right from both reactions.


Can we measure a potential of an electrode?

We can never measure the potential of an electrode there is no change in one single electron in a solution.

So we have Standard hydrogen electrode which its potential is O and other electron potentials are measured by that..









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