NCERT 8th Class (CBSE) Science: Chemical Effects of Electric Current

Question: For electroplating copper on an iron object, which terminal of the battery is connected to the iron objects?

Answer: Negative terminal of the battery.

Q14. In the process of purification of copper metal, a thin plate of pure copper & a thick rod of impure copper are used as electrodes & a metal salt solution is used as an electrolyte:
a) Which electrode is connected to the positive terminal of the battery?
b) Which electrode is connected to the negative terminal of the battery?
c) Which metal salt solution is taken as electrolyte?

Answer: a) Thick rod of impure copper. b) Thin rod of pure copper. c) Copper sulphate solution.

Question: Write down the important points which should be remembered while electroplating?

Answer: The important points to remember while electroplating:

1. The metal on which electroplating is to be done should be cathode i.e., the negative electrode.
2. The metal to be deposited should be anode i.e., the positive electrode.
3. A water soluble salt of the ‘metal to be deposited’ is taken as the electrolyte.

Question: On what factors the chemical effect produced by an electric current depends?

Answer: The chemical effect produced by an electric current depends on the nature of conducting solution (through which it is passed), & on the nature of electrodes used for passing the electric current.

Question: What is electricity?

Answer: Electricity is a phenomenon known for its effect like chemical effect, Heating effect and magnetic effect.

Question: What is the cause of electricity?

Answer: The flow of charge is the main cause of electricity.

Question: What is charge?

Answer: The fundamental properties of matter caused by gain or loss of electrons.SI unit of charge is Coulomb or C.

Question: What is the charge on 1 electron?

Answer: 1.6 x 10-19C

Question: How many electrons present in 1 coulomb charge?

Answer: 6.2 x 10^18 electrons and 5.7 x 10^-12 kg respectively. Charge of e = 1.6 x 10^-19 C Mass of e = 9.1 x 10^-31 kg.