Chemical Effects Of Current – Short Questions Collection With Answer | Physics Class 12

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Chemical Effects Of CurrentVery Important Questions Collection
HSEB | Science Faculty
Chemical Effects Of Current – Physics Grade XII
Short Questions with Answer (Solution)

1. What are the current carriers in solid conductors, liquids and gases?
Ans. The rate of flow of electric charges particle per unit time in a definite direction is called electric current. There are different substances as given below:

  • Free electrons are the current carriers in solid conductors.
  • Positive and negative ions are current carriers in conducting liquids.
  • Electrons and positive ions are current carriers in gasses.

2. Distinguish between ionic and electronic conduction.
Ans. The differences between ionic and electronic conduction are:

  • Ionic conduction is possible only inside the electrolyte while the electronic conduction is possible inside the metallic conductor as well as semiconductor.
  • The number density (n) of ions in an electrolyte is very small as compared to that of free electrons in a metallic conductor.
  • The drift velocity of ions in ionic conduction is smaller than small of electrons in electronic for a given electric field.
  • The resistance offered by the solution to ions in ionic conduction is much more than that offered by the metal to the drifting free electrons in electronic conduction.

3. How do you distinguish between the passage of electric current through metal and that through metal and that electrolyte?
Ans. When electric current passes through a metal, the charge carriers are free electrons but when it passes through an electrolyte, the charge carriers are both positive and negative ions. Thus, by identifying the charge carriers, one can distinguish between the passenger of electric current through metal and that through electrolyte.

4. The conductivity of an electrolyte is low than that of a metal. Why?
Ans. The conductivity of an electrolyte is low than that of a metal because:

  1. The density of free ions in an electrolyte is much less than that of free electrond in metals.
  2. The drift velocity of ions is smaller than that of electrons in a metal.
  3. The resistance of electrolyte is much higher than that of a metal.
    Being so, the conductivity of electrolyte is about 10power-5 times less than that of a metal.

5. What are the Faraday’s laws of electrolysis ?
Ans. There are two Faraday’s laws of electrolysis:

  1. First Law : The mass of the substance liberated or deposited on an electrode during electrolysis is directly proportional to the quantity of electric charge passed through the electrolyte.
    i.e. m ~ q => m = Z q
    Where Z is a constant and is called electrochemical equivalent (ECE) of the substance.
  2. Second Law : If the same quantity of electric charge is passed through different electrolytes, the masses of the substance liberated or deposited are proportional to their chemical equivalents. i.e m~E. So, if E1 and E2 are chemical equivalent of two substances of masses m1 and m2, then M2/m1 =E1/E2 .

6. What is meant by Faraday’s constant ?
Ans. The quantity or change required to liberate one gram equivalent of a substance during electrolysis is called Faraday’s constant.In other words, it can also be defined , as the charge required liberating one mole of a monovalent element during electrolsis. Its value is 96500 Cmol-1.

7. Why does the electrolysis possible with direct current but not with alternating current ?
Ans. The process of decomposition of a substance into its constituents by the passage of an electric current is called electrolysis. It is possible only if direct current (DC) is applied.During electrolysis, the DC influences the ions to move in one particular direction only so that the ions can transfer the charge to the charge to the electrodes and current is established in the electrolyte. But, the alternating current (AC) changes its direction frequently, When such Ac is applied, the ions cannot reach the electrodes but remain wandering inside the electrode. So, electrolysis is possible only with DC but with AC.

8. Voltameter measures current more accurately than an ammeter. Why?
Ans. An ammeter has small value of resistance and it is connected in series to measure the electric current. Which can alters the value of current slightly in the circuit. But, the relation, i.e. I = m/ Zt. All quantities of this relation can be accurately measured. That’s why, a voltameter measures electric current more accurately than an ammeter.

9. Why is Leclanche cell preferred in Meter Bridge and PO Box experiment but not in potentiometer experiment ?
Ans. Leclanche cell is a simple cell with e.m.f. about 1.5 V and low value of discontinuous current. In Meter Bridge and P O box, such low value of e.m.f. and current is sufficient. But, in potentiometer experimental, steady current is required, which can’t be obtained by this cell. That’s why, Leclanche cell is preferred in Meter Bridge and P O box experimental but not in potentiometer experiment.

10.The pure HCL is a bad conductor but the solution of HCL in water conducts electricity. Explain.
Ans. The pure HCL is a bad conductor of electricity. But when HCL is dissolved in water, it decomposes into H+ and Cl ions due to high relative permittivity of water. Those ions conduct electric current by making the solution a good conductor.

11. What is the function of charcoal and manganese dioxide used in the porous pot Leclanche cell?
Ans. The function of charcoal and manganese dioxide used in the porous pot of Leclanche cell is as oxidizer. Here , manganese dioxide oxidizes layer of hydrogen ions and removes the back e.m.f. provided by hydrogen ions and other metallic components. It removes the polarization effect. Moreover, charcoal reduces the internal resistance of cell by making the manganese dioxide electrically conducting.

Posted By : Hari Prasad Chaudhary | Comment RSS | Category : Class XII, HSEB Notes
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