NCERT Solutions For Class 8 Science Chapter 11 Chemical Effects Of Electric Current LAQs
Question 1. In the circuit given in the figure, Boojho observed that copper is deposited on the electrode connected to the negative terminal of the battery. Paheli tried to repeat the same experiment, but she could find only one copper plate. Therefore, she took a carbon rod as the negative electrode. Will copper still be deposited on the carbon rod? Explain your answer.
Answer: Copper will not be deposited on the carbon rod because, carbon rod is a poor conductor of electricity. For electroplating, the circuit must be completed, and that can be completed only by using the conducting material. Instead of a carbon rod, it should be any metal, then only it can be electroplated.
NCERT Class 8 Science Chapter 11 Chemical Effects of Electric Current LAQs
Question 2. Observe the circuit given in the figure
Boojho set up this circuit for the purification of copper. What will be the nature of (a) plate A, (b) plate B (c) the solution? Explain the process of purification.
Answer:
We take CuS04 solution and dip a pure copper plate as the cathode (-ve) and an impure copper plate as the anode (+ve). Due to the voltage of the battery, the impurities from the impure sample slowly deposit at the bottom, and the copper plate becomes purified.
NCERT Solutions for Chemical Effects of Electric Current Chapter 11
Question 3. The process that you saw in Activity 7 is used for the purification of copper. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from the impure rod is sought to be transferred to the thin copper plate. Which electrode should be attached to the positive terminal of the
battery and why?
Answer:
The impure rod of copper should be attached to ihe positive terminal of the battery and pure copper plate should be attached to the negative terminal of the battery.
When electric current is passed through the copper sulphate solution, copper sulphate dissociates into copper and sulphate ions The free copper gets drawn to the electrode connected with negative terminal of the battery and starts depositing on it.
From the other electrode, a thick rod of impure copper, an equal amount of copper gets dissolved into the solution. Hence, the loss of copper from the solution is restored and the process continues. Thus, copper gets transferred from one electrode to the other.