Question

The metals at the top of the reactivity series can be obtained by:
A. reduction of their oxides
B. oxidation
C. electrolysis of their molten chlorides
D. heating

Answer 1

Hint: Reactivity series, also known as activity series, tells us the reactivity of metals of the periodic table. This series is written in such a way that a more reactive metal comes before and at the top of the less reactive metal. Hydrogen comes in between this series to compare the reactivity of metals.

Complete answer:
The reactivity series of metals consist of the most reactive metals at the top and that of the less reactive metals at the bottom. The top most metals are so reactive that they even react in air or moisture. These metals are sodium, potassium, calcium etc.
As the reactivity of the metals at the top is very high, they cannot be extracted by their oxides on reduction. So, a method of electrolysis is used to obtain these highly reactive metals.
The extraction of highly reactive metals involves the electrolysis of their chlorides. The electrolysis is carried in the molten state. For example, electrolysis of NaCl is done to obtain sodium metal. These get deposited on the cathode of the electrolysis set up.
Hence, metals at the top of the reactivity series can be obtained by electrolysis of their molten chlorides.

So option C is correct.

Note:
Electrolysis involves the electrode potential of ions that make them deposit at the electrodes, or to get released in the form of gases. The high reactivity of metals does not make oxides with carbon, or they are not obtained by heating as they will react with oxygen during combustion.