Chapter 16 : Electric Current and It's Chemical Effect
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1. Most liquids, that conduct electricity, are
solutions of ________, ________ and ________.
ANS: acids, bases and salts
2. The ________ the concentration of an ion in the
solution, the greater is the conductivity of the solution.
ANS: greater
3. The passage of an electric current, through a
solution, can cause ________ effects.
ANS: chemical
4. When electric current is passed through copper
sulphate solution, copper gets deposited on the plate connected to the ________
terminal of the battery.
ANS: negative
5. The process, in which electricity is used to
deposit a thin layer of any desired metal on another metallic object, is known
as ________.
ANS: electroplating
6. The faster is the relative motion between the
magnet and the (closed) coil, the ________ is the current that flows through
the coil.
ANS: greater
1. A solution of silver nitrate is a good electrolyte.
ANS: True
2. An electrolytic cell consists of a cathode, anode
and an electrolyte.
ANS: True
3. Oxygen gets liberated at the anode during the
electrolysis of acidified water.
ANS: True
4. Electrorefining is the process of coating one metal
on another using an electric current.
ANS: False
5. The phenomenon of ‘Electro-magnetic Induction’ was discovered
by the Italian Scientist, Alessandro Volta.
ANS: False
1. The names of four electrolytes are given below:
(A) sea water
(B) tap water
(C) nitric acid
(D) oxalic acid
Out of these, the weak electrolytes are the ones
labelled as—
•
A and B
•
B and C
•
B and D
•
A and D
ANS: B and D
2. Electrolytes conduct electricity due to the
movement of—
•
the
electrolyte itself.
•
electrons
only.
•
positive as
well as negative ions.
•
the electrodes
themselves.
ANS: positive as well as negative ions.
3. The electrode, connected to the positive terminal
of a battery, is known as the—
•
anode
•
positive pole
•
cathode
•
electrorefiner
ANS: anode
4. The phenomenon of decomposition of an electrolyte,
when electricity is passed through it, is known as—
•
conduction
•
coating
•
electrolysis
•
electrorefining
ANS: electrolysis
5. The process, of coating of (say) iron with
chromium, is known as—
•
extraction
•
electrolysis
•
electroplating
•
electrorefining
ANS: electroplating
1. State the appropriate term, used for a liquid or
solution, which can conduct electricity (along with some accompanying chemical
changes).
ANS:
A liquid or solution that can conduct electricity
along with accompanying chemical changes is called an electrolyte.
2. Distinguish between strong and weak electrolytes.
Give two examples of each.
ANS:
(a) Strong electrolytes ionise completely in solution
and conduct electricity well, whereas weak electrolytes ionise only partially
and conduct electricity poorly.
(b) Examples of strong electrolytes are sodium
chloride solution and copper sulphate solution.
(c) Examples of weak electrolytes are acetic acid and
ammonium hydroxide.
3. Name the device that converts—
(a) Chemical energy into electrical energy.
ANS: Voltaic cell
(b) Mechanical energy into electrical energy.
ANS: Electric generator
4. Name the scientists who introduced the (scientific)
world to the—
(a) voltaic cell
ANS: Alessandro Volta
(b) phenomenon of electrolysis
ANS: Michael
Faraday
(c) phenomenon of electro-magnetic induction
ANS: Michael
Faraday
5. An Electrode ‘A’ is connected to the positive terminal while Electrode ‘B’ is connected to the negative
terminal of a battery, as shown in the diagram.
(a) Give the names of Electrodes A and B.
ANS:
Electrode A is the anode and Electrode B is the
cathode.
(b) Name the process associated with the circuit shown
here.
ANS: Electrolysis of water
(c) Name the gases produced at A and B.
ANS:
Oxygen is produced at A and hydrogen is produced at B.
6. State the meaning of the terms:
(a) Electro-magnetic induction
ANS:
The phenomenon of generating electric current by
changing the magnetic field around a conductor is called electro-magnetic
induction.
(b) Electrolysis
ANS:
The process of decomposition of an electrolyte by
passing electric current through it is called electrolysis.
(c) Electrodes
ANS:
Electrodes are metallic rods or plates through which
electric current enters or leaves an electrolyte.
(d) Electrorefining of metals
ANS:
Electrorefining is the process of purification of
metals using electricity.
7. State three uses of the phenomenon of electrolysis.
ANS:
(a) Extraction of metals from ores.
(b) Purification of metals.
(c) Electroplating of metals.
1. Give reasons for the following:
(a) Solid sodium chloride does not conduct electricity
while sodium chloride solution conducts.
ANS:
In solid sodium chloride, ions are not free to move
and hence electricity cannot pass through it. In sodium chloride solution, free
ions are present and these ions conduct electricity.
(b) It is not safe to carry out electrical repairs
outdoors during a heavy downpour.
ANS:
Rainwater generally contains dissolved salts and conducts electricity. Therefore, there is a risk of electric shock during a heavy downpour.
(c) To carry out electrolysis of water, a few drops of
sulphuric acid are (carefully) added to the water.
ANS:
Pure water is a poor conductor of electricity.
Sulphuric acid provides ions to the solution and increases its conductivity.
(d) Kitchen gas burners are often coated with
chromium.
ANS:
Chromium coating prevents corrosion, provides shine
and increases the durability of the burners.
2. Three electrolytic cells A, B and C are connected
with identical bulbs in separate circuits as shown in the diagram. Electrolytic
cell A contains sodium chloride solution and Electrolytic cell B contains
acetic acid. The electrolytic cell C contains distilled water.
(a) In which Set-up will the bulb glow the brightest?
ANS:
The bulb will glow brightest in Set-up A because
sodium chloride solution is a strong electrolyte.
(b) In which Set-up will the glow of the bulb be quite
dim?
ANS:
The bulb will glow dimly in Set-up B because acetic
acid is a weak electrolyte.
(c) In which Set-up will the bulb not glow at all?
ANS:
The bulb will not glow in Set-up C because distilled
water is a poor conductor of electricity.
3. Ramit set-up the circuit shown below for
purification of Copper:
(a) Name the metals used for Electrodes A and B.
ANS:
Electrode A is impure copper and Electrode B is pure
copper.
(b) Name the process of purification.
ANS:
Electrorefining
(c) Name the solution that needs to be used.
ANS:
Copper sulphate solution
4. Define ‘electroplating’. How can steel spoons be plated with silver? Explain with the
help of a diagram.
ANS:
Electroplating is the process of depositing a thin
layer of a desired metal on another metallic object by using electric current.
For silver plating of steel spoons:
(a) The steel spoon is made the cathode and a silver
plate is made the anode.
(b) Silver nitrate solution is used as the
electrolyte.
(c) When electric current is passed through the
solution, silver gets deposited on the steel spoon.
5. Describe an experiment to show that we can get
electrical energy by using a magnet.
ANS:
(a) Take a hollow cylindrical pipe and wind insulated
copper wire around it to form a coil.
(b) Connect the ends of the wire to a bulb.
(c) Move a bar magnet rapidly towards the coil.
(d) The bulb glows momentarily, showing that electric
current is produced.
(e) This demonstrates that electrical energy can be
generated using a magnet.
6. A coil of insulated copper wire is connected to a
torch bulb. State the likely ‘response’ of the bulb, if a bar magnet is—
(a) pushed into the coil?
ANS:
The bulb will glow momentarily.
(b) pulled out of the coil?
ANS:
The bulb will glow momentarily again.
(c) held stationary within the coil?
ANS:
The bulb will not glow because no current is induced..
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