CG SCERT Chhattisgarh State Board Class 8 Science & Technology Chapter 11 Chemical Effects of Electric Current Exercises Questions and Answers.
Tick the correct answer.
(1) Which of the following is not a good conductor of electricity-
(a) Distilled water
(b) Lemon juice
(c) Salty water
(d) Tap water
Ans-a) Distilled water
(2) The electrolyte used in a simple voltaic cell is –
(a) Dilute sulphuric acid
(b) Dilute hydrochloric acid
(c) Copper sulphate solution
(d) Potassium hydroxide solution
Ans-b) Dilute hydrocholoric acid
(3) The process of depositing a layer of any desired metal on another material by means of electricity is known as-
(a) Electrolysis
(b) Electroplating
(c) chemical reaction
(d) Electro refining
Ans- b) electroplating
(4) The apparatus used for electrolysis is –
(a) Electric cell
(b) Voltmeter
(c) Ammeter
(d) Magnetic needles
Ans-b) voltmeter
Fill in the blanks
- Solution of — electrolyte is used in simple voltaic cell.
Ans-
- On passing current through any solution ,produces —- effect
Ans-chemical effect
- In solar cell—– energy is converted into —– energy.
Ans-solar energy into electrical energy
- Process of coating of expensive metals over cheap metals by voltaic cell is called—–
Ans-electroplating
- —–cells are used in watches ,calculator, transistors and artificial satellities.
Ans-solar cells
Answer the following questions.
- Does distilled water conduct electricity? If not what can we do to make it a conductor?
Ans-distilled water is not conduct electricity. But if we want to make distilled water conduct electricity then add a small quantity of salt in it then this water conducts electricity and become good conductor.
- In case of fire ,before the fireman uses the water they shut off the main electrical supply for the area. Explain why they do this?
Ans-in case if fire before the fireman uses the water they shut off the main electrical supply for the area because water is the good conductor of electricity.
- Explain the process of electrolysis?
Ans-electrolysis is the process of current flowing externally from anode to cathode but internally conducting solution current flows from cathode to anode this process is known as electrolysis. Electrolysis passes current through anode and cathode ions.
- Name the elctrolytical , positive terminal and negative terminal of button cell.
ans- In button cell followings terminals and electrolyte is there-
Electrolyte is sodium or potassium oxide.
Positive terminal is zinc or aluminium anode
Negative terminal is silver oxide or mercury oxide cathode.
- Write three uses of electroplating.
Ans-1. Electroplating is used to obtain pure metals from their ores.
- electroplating is used in ornaments.
3. tin cans used for storing food and they are made from electroplating.