Electrochemistry – IElectrochemical Cells

For GCE(O/L)

& IGCSE

students

• Reduction - Gaining electrons• Oxidation - Losing electrons

Mnenomic- “OIL RIG”»Oxidation is Losing»Reduction is Gaining

• The reactions in which oxidation occurs with reduction are REDOX REACTIONS.

Redox Reactions

Need to know

• Electrodea conductor through which electricity enters or leaves an object, substance, or region.

Electrodes

• Anode - Electrode at which the oxidation half reaction occurs

• Cathode - Electrode at which the oxidation half reaction occurs

•Electrolyte - a substance that produces an electrically conducting solution when dissolved in a polar solvent; water

Electrochemical cells• Converts chemical energy

into electrical energy• In a simple cell

– Two electrodes connected by a wire

– An acidified solution as the electrolyte

• Current passes from cathode to anode(from positive terminal to negative terminal)

Electrodes of a Simple CellAnode

• One electrode is the anode

• More reactive metal becomes the anode

• Oxidation half reaction occurs at anode

• Negative terminal

Cathode

• Other electrode is the cathode

• Less reactive metal becomes the cathode

• Reduction half reaction occurs at cathode

• Positive terminal

A Simple Electrochemical Cell

Activity- 1

Materials required•A small beaker•Diluted sulphuric acid•A zinc metal strip

Method •Add the diluted sulphuric solution to the beaker•Dip a part of the zinc strip into the solution

Continued..

Observations •Zn strip dissolve•Gas bubbles are liberated at the Zn strip

Continued..

• Oxidation half reaction• Zn(s) Zn2+

(aq) + 2e

• Reduction half reaction• 2H+ + 2e H2(g)

• Balanced ionic equation • Zn(s) + 2H+ Zn2+

(aq) + H2(g)

• Completed balanced reaction• Zn(s) + H2SO4(aq) ZnSO4(aq) + H2(g)

Activity - 2

• Observations•Zn strip dissolve•Gas bubbles are liberated at the Cu strip

Cont.

• ConclusionsZn(s) Zn2+

(aq) + 2e oxidation2H+ + 2e H2(g) reduction

• Balanced ionic equation Zn(s) + 2H+ Zn2+

(aq) + H2(g)

Negative terminal

At cathodeCu

Positive terminal

Activity - 3

• Observations•Iron strip dissolve•Gas bubbles are liberated at the Cu strip

uFe Cu

Cont.

• ConclusionsFe(s) Fe2+

(aq) + 2e oxidation2H+ + 2e H2(g) reduction

• Balanced ionic equation Fe(s) + 2H+ Fe2+

(aq) + H2(g)

Negative terminal

At cathodeCu

Positive terminal

Activity - 4

• Observations•Zn strip dissolve•Gas bubbles are liberated at the Cu strip

Cont.

• ConclusionsZn(s) Zn2+

(aq) + 2e oxidation2H+ + 2e H2(g) reduction

• Balanced ionic equation Zn(s) + 2H+ Zn2+

(aq) + H2(g)

Negative terminal

At cathodeFe

Positive terminal

Thank You!