chapter 6d voltaic cells class

8/8/2019 Chapter 6d Voltaic Cells Class

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Voltaic CellsVoltaic Cells


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Objectives :

By the end of the lesson, students should be able to

(a)Describe the structure of a simple voltaic cell.

(b)Explain the production of electricity from simple voltaiccell.

(c) Explain the reactions in a simple voltaic cell &

Daniell cell.

(d)Describe the differences between electrolytic cell &

voltaic cell.


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Voltaic Cells

Device that converts

chemical energy electrical energy.

Chemical reactions that take place

inside the cell cause the flow of e,

thus electricity is produced.


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Simple voltaic cell consists of

(a) two different metals(b) an electrolyte

Zinc


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Production of electricity in the cell will

cause the needle ofvoltmeter /

galvanometerdeflect.

Voltaic cell is also known as galvanic cell.


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Positive terminal(less reactive

metal)

CuZn

Dilute H2

SO4

Zn Zn2+ + 2e Cu2+ + 2e Cu

Negative terminal

(more reactive

metal)

zinc Copper cell

Simple cell with zinc and copper


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Zn higher than Cu in the

electrochemical series.

Zn releases e more

easily than Cu.

Zn atom donates 2e to

form Zn2+ ion in thesolution while e go onto

zinc electrode to make it

negatively charged.

At negative terminal :

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


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e flow through external

circuit towards the Cu

plate which act as thepositive terminal.

Cu2+ ion which is lower

than Zn2+

ion in theelectrochemical series, is

selectively discharged to

form copper metal.

At positive terminal :

Cu2+(aq) + 2e Cu(s)


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Overall equation :

Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s)

This set up will form an electric cell

through chemical reaction.

Flow of electron from negative

terminal(anode) to positive terminal (cathode)


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Type of metal Voltage (V)

Zn/Cu 2.7

Cu/Cu 0.0


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Concentration of CuSO4

solution

decreases (blue solution becomes paler)

Concentration of ZnSO4solution increases

Daniell Cell

Ano

de-negative

terminal

Catho

de-positive

terminal


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A salt bridge is made from a piece of filter

paper soaked in a saturated solution which

does not interact with the 2 electrolytes.

Example of saturated solutions :KNO3, NaNO3, dilute H2SO4.


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Concentration of CuSO4

solution

decreases (blue solution becomes paler)

Concentration of ZnSO4solution increases

Daniell Cell


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Zn is higher than Cu in the electrochemical series.Thus, Zn releases e more easily than Cu.

Negative terminal (anode):

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

Positive terminal (cathode):

Cu2+(aq) + 2e Cu(s)

Overall equation :

Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s)


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Intensity of the blue colourof theCuSO4 solution decreases as the

concentration of Cu2+ ions decreases

gradually.


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Various type of voltaic cells :

(a) Dry Cell


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(b) Alkaline Batteries


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(c) Mercury Cell


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(d) Lead-acid Accumulator


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(e) Nickel-cadmium Batteries


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Disadvantages of voltaic cells

Corrosive & poisonous.

Cause pollution

Must be discard systematically.


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similarities

Electrolytic cell vs voltaic cell

An electrolyte

2 electrodes

Electron flow :Anode cathode

Donation of e : anode

Acceptance of e : cathode


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Voltaic CellElectrolytic Cell


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Not making our parents worry

is what it means to be a good

son or daughter.

~ Still Thoughts

chapter 6d voltaic cells class

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