define electrode according to lakhmir singh science class 8 chemical effects of electric chapter
Answers
Explanation:
Question 1.
Do liquids also conduct electricity?
Answer:
Liquids do conduct electricity, when they have free ions available like in case of Acids, Bases and Salts being dissolved in water.
Question 2.
Name two liquids which conduct electricity and two liquids which do not conduct electricity.
Answer:
Tap water and lemon water conduct electricity, this happens because tap water. while distilled water and wine do not conduct electricity.
Question 3.
Name a device which glows even when a weak electric current passes through it.
Answer:
A Light Emitting Diode (LED) glows even when a weak electric current passes through it.
Question 4.
Write the full form of LED.
Answer:
Light emitting Diode (LED)
Question 5.
How would you classify lemon juice- a good conductor or a poor conductor of electricity?
Answer:
Lemon juice is a good conductor of electricity. Lemon is a citrus fruit containing citric acid. Acids give H+ ions when dissolved in water, these free cations and anions make lemon juice a good conductor.
Question 6.
Vinegar is a sour liquid. State whether vinegar will conduct electricity or not.
Answer:
Vinegar is a poor conductor of electricity because it does not have any free ions to carry electric charge and conduct electricity.
Question 7.
What effect does an electric current produce when flowing through a conducting liquid (or conducting solution)?
Answer:
When electric current passes through a conducting liquid, it gets decomposed into ions. The conducting solution has free ions available which conduct electricity.
Question 8.
When electric current is passed through acidified water, then hydrogen and oxygen are formed. What type of effect of current is illustrated by this statement?
Answer:
When electric current is passed through acidified water, it dissociates water into H+ and OH– ions. This process is called chemical effect.
Question 9.
Acidified water is electrolyzed by using carbon electrodes. What is produced at:
(a) positive carbon electrode?
(b) negative carbon electrode?
Answer:
(a) Oxygen Gas is produced at positive carbon electrode.
(b) Hydrogen gas is produced as negative carbon electrode.
Question 10.
Give one example of the chemical effect of electric current.
Answer:
When an electric current is passed through a conducting solution, then chemical reactions take place in the solution. These chemical reactions cause chemical effects in the solution.
Example: When an electric current is passed through water, then water dissociates into hydrogen and oxygen. The chemical reaction is shown below: H2O → H+ (aq) + OH– (aq)
Question 11.
What should be done to decompose water into hydrogen and oxygen?
Answer:
Electric current must be passed through water to decompose water into hydrogen and oxygen.
Question 12.
Name the process in which a coating of one metal can be deposited on the surface of another metal by using current from a battery.
Answer:
Electroplating is the process in which a coating of one metal can be deposited on the surface of another metal by using current from a battery. The metal that needs to be deposited is used as the cathode while the metal on which it is deposited is used as anode. We use the salt of the cathode as the electrolyte.
Question 13.
Name the metal which is usually electroplated on car parts such as bumpers and bicycle handlebars made of steel.
Answer:
Chromium is electroplated on car parts such as bumpers and bicycle handlebars made of steel.
Question 14.
Which metal is electroplated on iron for making ‘cans’ used for storing food?
Answer:
Tin is electroplated on iron for making ‘cans’ used for storing food.
Question 15.
Name two metal objects which have a coating of another metal.
Answer:
Chromium is electroplated on other metals.
Gold is electroplated on other cheap metals.
Question 16.
Name the most common application of the chemical effect of electric current.
Answer:
The two most common examples of the chemical effect of electric current are:
Gold Coating on cheap metals
Electroplating of chromium metal to avoid corrosion.
Question 17.
Name two metals which are usually electroplated on cheaper metals for making jewelry (or ornaments).
Answer:
Gold and silver are electroplated on cheaper metals for making jewelry or ornaments.
Question 18.
Which is the polluting waste generated by electroplating factories?
Answer:
The conducting solution used in the electroplating process is the waste generated by electroplating factories.
Question 19.
Give a list of five objects around you which are electroplated.
Answer:
The list of five objects around you which are electroplated is:
Kitchen utensils.
Jewelry
Car parts
Cans
Taps
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