Question

When current is passed through molten sodium chloride
A. Sodium is deposited at a positive electrode and chlorine gas is deposited at the negative electrode.
B. Sodium is evaporated and chlorine ions are formed at the negative electrode.
C. Sodium is deposited at the positive electrode and chlorine is deposited at the negative electrode.
D. Sodium is deposited at the negative electrode and the chlorine gas is formed at the positive electrode.

Answer 1

Hint:Recall the basics of the process electrolysis. Using the basic information of the process of electrolysis, guess what may happen to the molten solution of the salt of sodium chloride. Also, check depending on the charges of the sodium and chlorine ions, on which electrodes these ions get deposited.

Complete answer:
The process in which a salt gets dissociated into its constituent ions when an electric current is passed through the solution of the salt is known as electrolysis.

Sodium chloride is a salt made of the elements sodium and chlorine.

When an electric current is passed through the molten solution of the sodium chloride, the elements constituting sodium chloride i.e. sodium and chlorine get separated in the form of their ions in the solution.

The sodium ion (\[{\text{N}}{{\text{a}}^ - }\]) has a positive charge and chlorine ion (\[{\text{C}}{{\text{l}}^ - }\]) has a negative charge.

The sodium ion being positively charged gets attracted towards the negative electrode i.e. cathode and the reduction reaction occurs between this positive sodium ion and electron and the sodium ion gets deposited on the cathode.
\[{\text{N}}{{\text{a}}^{\text{ + }}}{\text{ + }}{{\text{e}}^{\text{ - }}} \to {\text{Na}}\]

The chlorine ion being positively charged gets attracted towards the positive electrode i.e. anode and the oxidation reaction occurs of this negative chlorine ion with release of an electron and the chlorine ion gets deposited on anode.
\[{\text{C}}{{\text{l}}^ - } \to \dfrac{1}{2}{\text{C}}{{\text{l}}_2} + {{\text{e}}^{\text{ - }}}\]

Hence, the correct answer is option ‘D’.

Note:The students should keep in mind that the molten solution of sodium chloride salt carries an electric current but this flow of current is not due to the free electrons and is due to the free ions of sodium and chlorine. Also, the sodium in the solution of only sodium does not carry electric current in the solution.