Question

On electrolysis of molten sodium chloride, the gas evolved at anode is:
A. chlorine
B. hydrogen
C. nitrogen
D. hydrogen sulphide

Answer 1

Hint: We know that a cell has two oppositely charged terminals. The one which is connected to the positive end of the battery is anode and the other which is connected to the negative end of the battery is cathode. The battery helps in electrolysis.

Complete step by step answer:
We know that \[{\rm{NaCl}}\] comprises of \[{\rm{N}}{{\rm{a}}^ + }\] and \[{\rm{C}}{{\rm{l}}^ - }\] ions. During electrolysis, this molten will get break into positively charged \[{\rm{N}}{{\rm{a}}^ + }\] ion and negatively charged \[{\rm{C}}{{\rm{l}}^ - }\] ion. \[{\rm{N}}{{\rm{a}}^ + }\] ion will move towards cathode which is negatively charged and \[{\rm{C}}{{\rm{l}}^ - }\] ion will move towards anode which is positively charged. These ions undergo separate oxidation and reduction.
As anode helps in oxidation, \[{\rm{C}}{{\rm{l}}^ - }\] will get oxidized to \[{\rm{C}}{{\rm{l}}_{\rm{2}}}\] by losing electron.
As cathode helps in reduction, \[{\rm{N}}{{\rm{a}}^ + }\] will get reduced to \[{\rm{Na}}\] by accepting electrons.
Thus, chlorine gas is evolved at anode.

So, the correct answer is “Option A”.

Note:
We know that any non-feasible process or reaction does not occur on its own. There must be some external force that helps in carrying out this chemical change. This force is provided by a battery in electrolysis which breaks down the electrolyte into its corresponding ions. As electrolytic cells have cathode and anode, the electrolytic ions move to oppositely charged electrodes after electrolysis.