CBSE Class 8 Science Chemical Effect of Electric Current MCQs

Question. In LEDs, the longer lead (wire) is always connected to the _______ terminal
a) negative
b) neutral
c) positive
d) Any terminal

Answer: C

Question. Tap water is a good conductor of electricity while distilled water is not because
a) Tap water contain salts
b) Distilled water do not contain salt
c) Only a) is correct
d) Both a & b is correct

Answer: D

Question. When electrodes are immersed in water and electricity passed, the bubbles formed on the positive terminal is actually _______ gas.
a) Hydrogen
b) Carbon di oxide
c) Oxygen
d) Nitrogen

Answer: C

Question. When electrodes are immersed in water and electricity passed, the bubbles formed on the negative terminal is actually _______ gas.
a) Hydrogen
b) Carbon di oxide
c) Oxygen
d) Nitrogen

Answer: A

Question. Why do we add little dilute sulphuric acid to copper sulphate solution during electroplating?
a) To increase acidity
b) To increase conductivity
c) So that the colour becomes more prominent
d) To burn copper sulphate

Answer: B

Question. A coating of _________is deposited on iron to protect it from corrosion and formation of rust
a) copper
b) aluminium
c) Zinc
d) silver

Answer: C

Question. Chromium plating is done on many objects such as car parts, bath taps, kitchen gas stove etc. Why?
a) It does not corrode but prevents scratches
b) It looks beautiful
c) It costs less
d) Articles can be sold at higher price

Answer: A

Question. The process of depositing a layer of any desired metal on another material by means of electricity is called ___________.
a) Electric plating
b) Electroplating
c) Electric depositing
d) None of the above

Answer: B

Question. Some liquids are good conductors of electricity and some are poor conductors. Which one is a poor conductor?
a) Acidic solution
b) Alkaline solution
c) Common Salt solution
d) Distilled water

Answer: D

Question. Tin cans, used for storing food, are made by electroplating tin onto iron. Why?
a) Tin gives a shiny appearance
b) To make the vessel cheap
c) Tin is less reactive than iron.
d) To make the vessel lighter

Answer: C