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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!
