On this Page we have given West Bengal Class 8 English Medium Science Solution Chapter 2.4 Chemical Effects of Electricity Question and Answer for our Students of West bengal Class 8 English Medium. Hope this following Question Answer will help our Students.
West Bengal Class 8 | Science | Chemical Effects of Electricity
Q.1) MCQ
1) Electricians usually stand on a bamboo ladder while working on a live electrical line because
a) bamboo ladders are cheap
b) bamboo ladders are light
c) bamboo are poor conductors of electricity
d ) bamboo are hard and sturdy
Ans. bamboo are poor conductors of electricity
2) To test the conductivity of a liquid a led should be used instead of a bulb
a) a led can be easily fitted in a circuit
b ) a led can light up at low currents
c ) a led takes less space
d ) all of the above
Ans. A led can light up at low currents
3) Distilled water are very poor conductors of electricity due to the
a ) absence of salts and metal compounds
b) presence of salts and metal compounds
c) absence of dissolved gases
d) presence of dissolved gases
Ans. Absence of salts and metal compounds
4) The chemical change of a substance upon passage of electricity through a fused state or solutions is called _____
a ) electrolyte b) cathode b) anode d) electrolysis
Ans. Electrolysis
5) ______ are the compound which conduct electricity in fused state or in a solution.
a ) aqueous b) electrodes c) electrolytes d) ionic
Ans. Electrolytes
6) Except one electrolyte all others remains completely disassociated in water
a ) NaCl b) CH3COOH c)KOH d) H2SO4
Ans. CH3COOH
7) Which of the following substance is true about electrolytes
a ) anything that dissolves in water is electrolytes
b) anything that melts is an electrolyte
c) a substance must produce ion to be an electrolyte
d) both a and b
Ans. A substance must produce ion to be an electrolyte
8) The electrode connected to the positive terminal of the cell is called
a ) cathode b) anode c) lynode d) +node
Ans. Anode
9) The element which is not desired but happens to be produced after the electrolysis is known as
a ) by product of electrolysis b) by product
c) waste product d) remainder
Ans. By product of electrolysis
10) To remove the impurities from copper we must perform
a ) chlorination b) electrification c) electrolysis d) galvanization
Ans. Electrolysis
11) A metallic substance is generally electroplated by electrolysis process so that
a ) it can protected from the action of rust
b) to make the metal look attractive to the eyes
c) to make the metal heavier
d) both a and b
Ans. Both a and b
12) On the electrolysis of copper sulphate solution , a reddish brown coating gets deposited on iron(electrode) due to the
a ) the deposition of copper ions
b) the deposition of sulphur ions
c) the decomposition of iron
d) the corrosion of iron
Ans. The deposition of copper ions
13) The substances which needs to be coated is taken as _____
a ) anode b) cathode c) electrolyte d) either anode or cathode
Ans. Cathode
14) It’s best to coat iron with a layer of ____ to protect it from rusting
a ) copper b) silver c) aluminum d) zinc
Ans. Zinc
15) The correct way to differentiate between a nickel plated substance and an actual stainless steel is
a ) stainless steel is more sonorous
b ) stainless steel is more conductive
c) nickel plated substance is more attracted to magnet
d ) stainless steel is lighter
Ans. Nickel plated substance is more attracted to magnet
Q.2) Short answer questions.
(1) What Is flowing through the object when the bulb glows ?
→Electricity
(2) What do you mean by good conductor of electricity?
→When the electricity is passing through the conductor, then it will be said as good conductor of electricity.
(3) What is poor conductor of electricity?
→ When electricity is not passing through the conductor, then it is said as poor conductor of electricity.
(4) Explain about the conductivity of distilled water?
→ Distilled water is good conductor of electricity.
(5) Why the distilled water is good conductor?
→Because it contains number of salts and metal components which conducts electricity.
(6) Define electrolysis ?
→When chemical change of a substance occurs upon passage of electricity through a fused state or a solution is called as electrolysis.
(7) What are electrolytes ?
→The compounds which able to conduct electricity in the fused state or in a solution are called electrolytes.
(8) Give two examples of electrolytes.
→
- Aqueous solution of salts
- Fused NaCl
(9) Define strong electrolytes ?
→Some electrolytes remain completely dissociated in a solution are called as strong electrolytes.
(10) Define weak electrolytes ?
→ Some electrolytes remain ionized in a solution to the very small extent called as weak electrolytes.
(11) Give two examples of strong electrolytes ?
→
- NaCl
- KCl
(12) Give example of weak electrolytes ?
→
- Acetic acid
(13) What are non-electrolytes?
→ The substance which doesn’t produces ions in a fused state Or in a solution called as non-electrolytes.
(14) Give two examples of non-electrolytes.
→
- Water
- Urea
(15) What do you mean by electrodes ?
→Two metal wires may be of metal plate or graphite rods through which electricity will pass from the battery are called as electrodes.
(16) Name two things necessary for electrolysis ?
→
- Source of electricity
- Electrodes
(17) Define cathode .
→ The electrode connected to the negative end of the battery is called as cathode.
(18) Define anode .
→The electrode connected to the positive end of the battery is called as anode .
(19) Which reaction occurs at cathode?
→ Reduction reaction
(20) Which reaction occurs at anode ?
→ Oxidation reaction
(21) What do you mean by the byproduct of electrolysis?
→ The substance comes along the required product in an electrolysis called as byproduct of electrolysis.
(22) State two important uses of electrolysis ?
→
- Metal extraction
- Purification of metals
(23) What do you mean by electroplating?
→ Electrolysis used to give a metallic coating on another metal called as electroplating.
(24) Give one example of electroplating ?
→ To prevent rusting of iron , zinc metal is plated over the iron with the help of electrolysis.
(25) Gold is plated over the ornaments of silver, which acts as cathode in this case.
→ Ornaments of silver acts as cathode .
(26) Which electrode acts as anode in above case ?
→ Gold ( pure gold strips )
(27) Which metal is coated over parts of bicycle or a car ?
→ Chromium metal is coated over the parts of bicycle or a car.
(28) What is metal extraction?
→ Some metals are separated from their compounds by electrolysis called as metal extraction .
(29) Why fused salt is taken for the process of metal extraction ?
→Fused salt is taken because aqueous Solution of the salt cannot produce the metal by this method.
(30) Why metals are purified ?
→ Metals are present in their ore forms with all the impurities in it, hence to remove that impurities, metals should be purified.
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