Chemistry Presentation-chapter 6- Gogulan Group

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CHEMISTRYPRESENTATION( 4 ARIF/2011)

SEKOLAH MENENGAH KEBANGSAANPAYA KEMUNTING ,06000 JITRA , KEDAH DARUL AMAN.


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CHAPTER 6ELECTROCHEMISTR

Y(SIMPLE VOLTAiC CELL)


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An electrochemical cell which produceselectrical energy from the spontaneous

chemical reactions occuring inside it. Also called as galvanic cell or chemical cell.

The flow of an electric current occurs when two

electrical conducting materials with differentelectrical potential, are connected together viaa conducting wire.

Electric current travels from the conductor witha higher potential to the conductor with alower potential and this process of flow of

WHAT

ISSimple voltaic cell ?


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vo a cCELLS

Can be made by dipping two different types of metals inan electrolyte, and connecting the two metals by wires inthe external circuit.

The metals act as the electrodes. Electrodes are connected to a voltmeter, a galvanometer

or an electric bulb.

Conversion energy :

chemical energyelectrical energy

Chemical reactions inside the cell cause the flow ofelectron and electricity is produced.

The more electro ositive metal will release electrons


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vo a cCELLS

Electrons flow from the negative terminal to the positiveterminal of the cell through the external circuit producesan electric current.

Flow of electric current is detected by the lighting up of alight bulb or the deflection of a galvanometer needle.

The voltage of the cell or the potential difference of thecell is the electromotive force , e.m.f. that moves

electrons and can be measured by a voltmeter. The further the distance between the positions of two

metals in the electrochemical series, the bigger the cellvoltage. For example a Mg-Cu cell will produce highervoltage than Zn-Cu cell.


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Heart pacemakers have successfully prolonged the life ofmanypatientswith heart diseases. A heart pacemaker is made of a zinc-silver(Zn-Ag)cell. The cell is implanted under the patients chest and is wired directlyto the surface of the patient heart. The body fluids acts as electrolytes.

The cardiac pacemaker will be located in the wall of the right atrium.

Chemistry, Technology & Society(Extra Fact)


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Experiment


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e wor ng o asimple voltaic cell Materials : Zinc plate, Copper plate, copper (II) sulphate

solution,CuSo4 Apparatus : beaker, connecting wires with crocodile clips

and voltmeter.

Procedure :

1. A piece of zinc plate and a copper plate aren cleanedwith sandpaper.

2. The two pieces of metals are connected usingconnecting wires as shown in Figure 1.

3. Both plates are then immersed in copper (II) sulphatesolution,CuSo4 solution.

4. The reading of the voltmeter is recorded.

Figure 1


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Discussion :

1. Zn loses e- more readily than Cu ,as it is more electro(+)

than Cu. Each zinc atom loses two free electrons and hencegains two units of positive charge.

2. The zinc "half-reaction" is classified as oxidation since itloses electrons. The terminal at which oxidation occurs iscalled the "anode". For a battery, this is the negative

terminal.

Zn(s) -> Zn2+(aq) + 2e-

3. The electrons will then flow through the external circuit to Cumetal , producing an electric current.

4. The copper(II) ions from the CuSO4 solution receive electronsto form Cu metal.

5. The copper "half-reaction" is classified as reduction since itgains electrons.The terminal at which reduction occurs iscalled the "cathode". For a battery, this is the positiveterminal.
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Chemistry Presentation-chapter 6- Gogulan Group