Sunday, December 7, 2014

8th Chemical Effects of Electric Current solved Questions

Section: A
Q.1 A positively charged ion is called 
(A) atom (B) anion C) cation (D) neutral ion

Q.2 The instrument needed to measure the current flowing through a circuit is ? 
(A) voltmeter B) voltameter (C) galvanometer (D) ammeter

Q.3 The process in which any electrolyte gets decomposed when electricity is passed through it, is called 
(A) electrolysis (B) decomposition (C) dissociation (D) splitting

Q.4 The process of depositing a thin layer of any superior metal over an object of a cheaper metal with the help of electricity is called 
(A) electrorefining (B) electrometallurgy (C) electroplating (D) electrowinning

Q.5 Which of the following is the most essential for an electric circuit to work ? 
(A) A switch (B) An electric current (C) A switch board (D) none of these

Ans. 1.C                   2.D                   3.A                            4.C                       5.B


Q.1 What are conductors ?

Ans: Materials which allow electric current to flow through them are called conductors.

Q.2 What are insulators ?
Ans: Materials which do not allow electric current to flow through them are called insulators

Q.3 Why is distilled water conductor or an insulator ?

Ans: Distilled water is an insulator because there are no salts dissolved in it.

Q.4 What are electrodes ?

Ans:Electrodes are the terminals through which current is passed into a liquid.

Q.5 What is an electrolyte ?

Ans:An electrolyte is a liquid which is a good conductor of current.

Q.6 What happens when an electric current is passed through a conducting solution ?

Ans: A chemical reaction takes place when electric current is passed through a conducting solution.

Q.7 Define electroplating.

Ans: Electroplating is the process of depositing a layer of any desired metal on another metallic
object by means of electricity.

Q.8 Apart from chemical effect, which other effect electric current produce ?

Ans: Electric current can produce magnetic effect

Q.9 Name one non-metal which a good conductor of electricity ?

Ans: Graphite

Q.10 What is electrolysis ?
Ans: Electrolysis is the breaking up of a compound from its solution on passing electric current through the electrolyte.

Q.11 How can distilled water be made a good conductor of electricity ?

Ans: Distilled water can be made a good conductor of electricity by adding acid, base or salt to it.

Q.12 In what proportion the two products from electrolysis of water are obtained ?

Ans: By volume of hydrogen gas is twice the volume of oxygen gas.

Q.13 Why should you not touch electrical appliances with wet hands ?

Ans: Water is a solution of salts and so it is a good conductor of electricity. Therefore, we
can be electrocuted

Q.14 In case of a fire, before the firemen use the water hoses, they shut off the main electrical
supply for the area. Explain why they do this.

Ans: Firemen shut off the main electrical supply for the area because water is a good conductor of electricity and the firemen can get electrocuted

Q.15 Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour ? Explain.

Ans:No, it is not advisable for fire men to carry out electrical repairs during heavy downpour
because water is a good conductor of electricity and the fire person can get shock.

Q.16 What is the disadvantage of electroplating done in the factories ?

Ans: The disposal of the used conducting solution is hazardous and can cause environmental
pollution. There are specific disposal guidelines for environmental protection .

Q.17. Why is chromium used for electroplating ?

Ans: Chromium is used for electroplating because it has a shiny appearance, does not corrode
and is scratch resistant.

Q.18. Why the iron cans are electroplated with tin?

Ans: Tin is less reactive than iron. Thus food, stored in iron cans, is prevented from being spoilt by the iron by electroplating it by tin.

Q.19. After the electroplating of a spoon with silver, it was found that the anode has become thin why ?

Ans:During electroplating, the silver metal from the anode is deposited on the cathode. Therefore, it becomes thin.

Q.20. During electrolysis of water, why does hydrogen collect on cathode and oxygen collect on anode ?

Ans: When electric current is passed in water hydrogen ions (H+) move towards cathode and get collected over it. Hydroxyl ions (OH–) move towards the anode and oxygen is collected on it.

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