Chapter 2 Element, Compound And Chemical Chemical Effects Of Electricity SAQs
Question 1. What do you mean by electrolyte?
Answer:
Electrolyte:
This is the chemical compound which when dissolved in water produces ions and the solution becomes the conductor of electricity.
It undergoes dissociation when electricity is passed through It. The same word Is also commonly used to refer to a solution of all electrolytes in water. The term electrolyte solution is then used.
Question 2. What do you mean by strong electrolyte and weak electrolyte?
Answer:
Strong Electrolyte And Weak Electrolyte:
When dissolved in water or in a molten state, the electrolyte which produces a large number of ions is called the strong electrolyte.
For example, sodium chloride, sodium hydroxide, dilute sulphuric acid etc., are all strong electrolytes.
When dissolved in water or in a molten state, the electrolyte which produces a smaller number of ions is called a weak electrolyte. For example, acetic acid, ammonium hydroxide, etc., are all weak electrolytes.
Question 3. During electrolysis of water 10 cc oxygen collects at the anode, what and how much other substance collects at the cathode at that time?
Answer:
Electrolysis of water produces hydrogen and oxygen In the volumetric ratio of 2:1 as shown:
⇒ \(2 \mathrm{H}_2 \mathrm{O} \rightleftharpoons 2 \mathrm{H}_2+\mathrm{O}_2\)
Hence when 10 cc of oxygen collects at the anode; O2 ccs of hydrogen shall collect at the cathode at that time.
Question 4. An aqueous solution of ammonia is a weak electrolyte whereas sodium chloride is a strong electrolyte. Why?
Answer:
An aqueous solution of ammonia is a weak electrolyte whereas sodium chloride is a strong electrolyte:
Ammonia dissolves in water to produce ammonium hydroxide (NH4OH). In an aqueous medium, NH4OH dissociates to a very small extent to produce small numbers of NH4+ ions and OH– ions.
So it behaves as a weak electrolyte. An aqueous solution of sodium chloride dissociates completely to produce a large number of Na+ ions and Cl– ions. So it behaves as a strong electrolyte.
Read And Learn More WBBSE Solutions For Class 8 School Science Short Answer Type Questions
Question 5. Sugar, wax, butter, etc., are not electrolytes. Why?
Answer:
Sugar, wax, butter, etc., are not electrolytes:
To behave as an electrolyte, a substance should produce ions. But when sugar is dissolved in water, it does not produce any ions. Wax and butter are not soluble in water.
But even in their molten state also, they do not produce any ions. So they are not electrolytes.
Question 6. Why one should not touch an electric switch with a wet hand?
Answer:
Pure water does not conduct electricity. But usually, the water we use contains a significant concentration of salt, which make the water conductor of electricity. So, when one touches an electric switch with wet hands, one may experience an electrical shock.
Question 7. When electricians are working with a live wire, they usually stand on wooden tools. Why?
Answer:
Our body is a good conductor of electricity because our blood contains significant concentrations of different salts. So if one touches a live wire, then electricity passes through our body and touches the ground. It may cause even death to the concerned person.
But wood is a bad conductor of electricity. So when someone is standing on a wooden tool, the electric current cannot flow through the human body to touch the ground. Hence, no harm is done.
Question 8. How one can detect the flow of a very small amount of electricity flowing through an electrical circuit?
Answer:
To detect whether any small amount of electricity flowing through an electrical circuit or not, one has to place a magnetic needle pointing north-south, very near the electrical wire.
If even a very small amount of electricity flows through the wire, the magnetic needle is deflected, indicating the flow of electricity through the circuit.
Question 9. What do you mean by electroplating? Why it is done?
Answer:
Electroplating:
The process by which a thin layer of one metal is coated on the surface of the other to protect the latter from rusting or to improve its appearance is called electroplating.
For example, a thin layer of zinc is coated on the surface of the materials made up of iron to prevent it from rusting. Gold is electroplated on silver ornaments to give them a gold-like appearance. Metal fittings are plated with chromium to preserve their polish.
Question 10. What is the main, principle of electroplating?
Answer:
Main Principle Of Electroplating:
In the case of electroplating, the metal which is to be electroplated is used as the anode and the article on which the coating is given is used as the cathode, and a suitable salt solution is used as the electrolyte.
During electroplating, the pure metal from the anode is gradually dissolved as metal ions into the solution and the metal ions are deposited on the cathode material in the form of a thin film.
Question 11. What do you mean by galvanization? Why it is done?
Answer:
Galvanization:
The process of coating the surface of a material with a thin film of zinc is known as galvanization. Generally surface of the materials made up of iron is coated with zinc to prevent it from rusting.
Question 12. How can you differentiate a substance made of pure stainless steel from an iron substance electroplated with nickel?
Answer:
When an iron substance is coated with nickel, it appears like stainless steel.
So, it is difficult to visibly differentiate a substance made of pure stainless steel from an iron substance electroplated with nickel.
But stainless steel is not attracted by a magnet, but iron is. So when a magnet is brought closer to stainless steel objects it is not attracted, but the iron substances electroplated with a thin layer of nickel will be attracted towards the magnet.
Question 13. When molten sodium chloride or magnesium chloride or calcium chloride is electrolyzed using suitable electrodes, the respective metal is deposited at the cathode. But when an aqueous solution of the chloride salts of Na, Mg or Ca is electrolyzed, the metals cannot be extracted. Why?
Answer:
When molten sodium chloride or magnesium chloride or calcium chloride is electrolyzed using suitable electrodes, the respective metal is deposited at the cathode. But when aqueous
This is because, when an aqueous solution of metal halides is electrolyzed, both H+ ions and Metal ions move towards the cathode. But in this case, H+ ions are preferentially discharged at the cathode. As a result, hydrogen gas is formed at the cathode.
At the cathode (Reduction): \(2 \mathrm{H}^{+}+2 e \rightarrow \mathrm{H}_2\)