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Class 8 Practice – Level 3 – Set 1 – Chemical Effects of Electric Current
Total questions: 15
1.
In the process of electroplating, what is the primary purpose of using a direct current (DC) power source?
To prevent the formation of gas bubbles
To ensure uniform metal deposition on the object
To increase the temperature of the electrolyte
To minimize the cost of the electroplating process
None
2.
What is the effect of increasing the voltage during the electrolysis of a solution?
It decreases the rate of reaction
It causes less gas to be produced
It increases the rate of the chemical reactions at the electrodes
It prevents the breakdown of water
None
3.
During the electrolysis of sodium chloride solution, which gas is produced at the anode, and what reaction occurs there?
Oxygen, formed by the oxidation of water
Hydrogen, formed by the reduction of water
Chlorine, formed by the oxidation of chloride ions
Sodium, formed by the reduction of sodium ions
None
4.
What can be inferred if a liquid does not conduct electricity and the LED does not light up during testing?
The liquid is a good conductor
The liquid is a poor conductor
The liquid is an insulator
The liquid contains dissolved salts
None
5.
In an experiment using an LED to test various solutions, what does it indicate if the LED flickers weakly?
The solution is a strong acid
The solution has a low concentration of ions
The solution is pure water
The solution has high electrical resistance
None
6.
Why are concentrated sulfuric acid and concentrated sodium hydroxide considered good conductors of electricity?
They do not dissociate in water
They dissociate completely into ions when dissolved in water
They are neutral substances
They do not react with other chemicals
None
7.
What are some potential environmental impacts of improper disposal of materials used in electroplating?
Reduced soil fertility
Increased water temperature
Heavy metal contamination
Increased plant growth
None
8.
What principle explains why electrolysis can be used to separate metal from its ore?
Electrons are absorbed by the ore
Ions in the solution are attracted to the electrodes
The metal ions lose their charge at the anode
The heat from the reaction melts the ore
None
9.
What determines whether a solution conducts electricity or not?
The temperature of the solution
The amount of solute present
The presence of free-moving charged particles
The color of the solution
None
10.
When testing a liquid with an LED, which result indicates the presence of an electrolyte?
The LED is off
The LED lights up briefly
The LED glows steadily
The LED flickers
None
11.
Which of the following metals is most commonly used as the anode in the electroplating of gold?
Copper
Silver
Gold
Zinc
None
12.
What is the primary reason for adding a salt to water during electrolysis?
To increase the number of ions present in the solution
To increase the electrical resistance
To decrease the temperature of the solution
To change the pH of the solution
None
13.
During electrolysis of a molten ionic compound, what happens at the cathode?
Cations gain electrons and are reduced
Anions lose electrons and are oxidized
There is no reaction
Both cations and anions are produced
None
14.
What type of solution would you expect to conduct electricity the best?
Pure water
Distilled water
A strong acid solution
A sugar solution
None
15.
What role does the resistor play in an LED conductivity test circuit?
It increases the brightness of the LED
It protects the LED from excessive current
It decreases the resistance of the circuit
It helps identify the type of liquid
None
1 out of 15
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