chapter 6d voltaic cells class
TRANSCRIPT
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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