Chemical Effects of Electric Current Test - 1

Pure or distilled water is an insulator as it does not contain any salts or ions for the conduction of electricity.

Some liquids, such as oil and alcohol, do not dissociate into ions and hence, they do not conduct electricity, whereas vinegar contains acetic acid dissolved in water. It separates into ions, and thus vinegar conducts electricity.

When we add metallic salt to water, it dissociates into ions. Hence, water conducts electricity.

An LED bulb is a device which works on very small current and hence, it can be used to detect small currents. So, both A and B are correct and B is the correct explanation for A.

The brightness of the bulb depends upon the current passing through the bulb. Greater the current, greater would be the brightness of the bulb. It means that if the tester glows brightly in case of liquid A and dimmer in case of liquid B, then liquid A is a better conductor than liquid B.

The process of depositing a thin layer of a desired metal over a metal object with the help of electric current is called electroplating.

The metal object on which electroplating is to be done is made the negative electrode. It is connected to the negative terminal (cathode) of the battery.

The metal whose layer is to be deposited is made the positive electrode. It is connected to the positive terminal (anode) of the battery.

A water-soluble salt of the metal to be deposited is taken as the electrolyte.

During the purification of copper metal, a thick rod of impure copper metal is made the positive electrode or anode, i.e. it is connected to positive terminal of the battery. A thin strip of pure copper is made the negative electrode or cathode, i.e. it is connected to the negative terminal of the battery.

Copper sulphate (CuSO₄) can be taken as the electrolyte. On passing electric current, the copper dissolves from the impure anode into the electrolyte solution. The copper present in dissolved form in electrolyte gets deposited on the cathode in the pure form. The impurities are left behind in the electrolyte solution.

Sugar solution does not dissociate into ions, so it is not an electrolyte.

According to Faraday's law, 'The amount of mass deposited or liberated at an electrode is directly proportional to the amount of charge passed through the electrolyte.'

In a Zinc-Carbon cell, zinc reacts with ammonium chloride and zinc chloride is formed. The zinc container becomes thinner as the cell is used because zinc metal is oxidised to zinc ions. When the zinc case becomes thin enough, zinc chloride begins to leak out of the battery.