Chemical Effects of Electric Current

Q32. Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.

Ans. It is not safe for the electrician to carry out electrical repairs outdoors during heavy downpour because rainwater being a conductor of electricity may cause electrocution of the electrician.

Q33. A child staying in a coastal region tests the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?

Ans. The compass needle deflects more in the case of seawater because due to the presence of a large amount of dissolved salts in it, sea water is a much better conductor of electricity than drinking water.

Q34. What are the chemical effects of electric current?

Ans. When an electric current flows through a conducting solution, it causes following chemical change:

                         i.        Bubbles of gas or gases may be formed on the electrodes.

                        ii.        Deposits of metals may form on electrodes.

                       iii.        Changes in colour of solutions may occur.

Q35. A tester is used to check the conduction of electricity through two liquids, labeled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You would conclude that
(i) liquid A is a better conductor than liquid B.
(ii) liquid B is a better conductor than liquid A.
(iii) both liquids are equally conducting.
(iv) conducting properties of liquid cannot be compared in this manner.

Ans. (i) liquid A is a better conductor than liquid B.

Q36. What happens when electric current is passed through acidified water?

Ans. When electrodes are immersed in water, and a current is passed through acidified water, then oxygen gas is formed at the positive electrode which is connected to the positive terminal of the battery and hydrogen gas is formed at the negative electrode which is connected to the negative terminal of the battery.

Q37. Tap water conducts electricity whereas distilled water does not. Give reason.

Ans. Distilled water is a poor conductor of electricity because it does not contain any dissolved salts in it which can provide it ions to conduct electricity. The distilled water becomes a good conductor of electricity on dissolving a little salt in it. The water that we get from taps is not pure. It may contain several salts dissolved in it. This water is thus a good conductor of electricity.

Q38. Why is electroplating useful?

Ans. Electroplating is a very useful process. It is widely used in industry for coating metal objects with a thin layer of a different metal. The layer of metal deposited has some desired property, which the metal of the object lacks. For example, chromium plating is done on many objects such as car parts, bath taps, kitchen gas burners, bicycle handlebars, wheel rims and many others.

Q39. Paheli had heard that rainwater is as good as distilled water. So she collected some rainwater in a clean glass tumbler and tested it using a tester. To her surprise she found that the compass needle showed deflection. What could be the reasons?

Ans. Rainwater is said to be pure water. But when rainwater falls to the earth through the atmosphere, it dissolves acidic gases such as carbon dioxide, sulphur dioxide and nitrogen oxides to form acids such as carbonic acid, sulphuric acid and nitric acid. Due to presence of acids in it, rainwater becomes a conductor of electricity.

Q40. Prepare a list of objects around you that are electroplated.

Ans. Examples of electroplating

                         i.        Chromium plating is done on many objects such as car parts, bath taps, kitchen gas burners, bicycle handlebars, wheel rims and many others.

                        ii.        Jewellery makers electroplate silver and gold on less expensive metals.

                       iii.        Tin cans, used for storing food, are made by electroplating tin onto iron.

                       iv.        A coating of zinc is deposited on iron to protect it from corrosion and formation of rust.