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Karnataka Board PUCPUC Science 2nd PUC Class 12

Electrochemical Cells

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Estimated time: 5 minutes
Maharashtra State Board: Class 12

Key Points: Electrochemical Cells

Type Electrolytic Cell Galvanic (Voltaic) Cell
Energy conversion Electrical → Chemical Chemical → Electrical
Nature of reaction Non-spontaneous Spontaneous
Anode Positive Negative
Cathode Negative Positive
Electron flow Cathode → Anode Anode → Cathode
Salt bridge Not required Required

Electrolysis of NaCl

1. Molten NaCl:

  • Oxidation: Cl⁻ → Cl₂ (gas)

  • Reduction: Na⁺ → Na (metal)

  • Products: Na (cathode), Cl₂ (anode)

2. Aqueous NaCl:

  • Oxidation: Cl⁻ → Cl₂

  • Reduction: H₂O → H₂ + OH⁻

  • Products: H₂ (cathode), Cl₂ (anode), NaOH formed

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Electrochemistry [00:35:33]
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Related QuestionsVIEW ALL [73]

Read the passage given below and answer the questions that follow:

Oxidation-reduction reactions are commonly known as redox reactions. They involve transfer of electrons from one species to another. In a spontaneous reaction, energy is released which can be used to do useful work. The reaction is split into two half-reactions. Two different containers are used and a wire is used to drive the electrons from one side to the other and a Voltaic/Galvanic cell is created. It is an electrochemical cell that uses spontaneous redox reactions to generate electricity. A salt bridge also connects to the half-cells. The reading of the voltmeter gives the cell voltage or cell potential or electromotive force. If \[\ce{E^0_{cell}}\] is positive the reaction is spontaneous and if it is negative the reaction is non-spontaneous and is referred to as electrolytic cell. Electrolysis refers to the decomposition of a substance by an electric current. One mole of electric charge when passed through a cell will discharge half a mole of a divalent metal ion such as Cu2+. This was first formulated by Faraday in the form of laws of electrolysis.
The conductance of material is the property of materials due to which a material allows the flow of ions through itself and thus conducts electricity. Conductivity is represented by k and it depends upon nature and concentration of electrolyte, temperature, etc. A more common term molar conductivity of a solution at a given concentration is conductance of the volume of solution containing one mole of electrolyte kept between two electrodes with the unit area of cross-section and distance of unit length. Limiting molar conductivity of weak electrolytes cannot be obtained graphically.

  1. Is silver plate the anode or cathode?  (1)
  2. What will happen if the salt bridge is removed?  (1)
  3. When does electrochemical cell behaves like an electrolytic cell?  (1)
  4. (i) What will happen to the concentration of Zn2+ and Ag+ when Ecell = 0.   (1)
    (ii) Why does conductivity of a solution decreases with dilution?  (1)
    OR
    The molar conductivity of a 1.5 M solution of an electrolyte is found to be 138.9 S cm2mol-1. Calculate the conductivity of this solution.  (2)
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