Question

Oxidation number of sodium in sodium amalgam is:
A. +2
B. +1
C. -3
D. 0

Answer 1

Sodium amalgam is an alloy formed by mixing two metals. Since it is formed without any chemical reaction, the oxidation number of sodium does not change.

Complete step by step answer:
Sodium amalgam is prepared by melting metallic sodium in mercury. It is an exothermic reaction. Just like solutions are characterised by the amount of solute in water, amalgams are described by the amount of sodium used to form the amalgam and there is no particular chemical formula for the amalgam. Sodium has a single valence electron and in chemical reaction it generally loses its electron to form ionic bonds and form compounds. In those cases, sodium will have an oxidation number of +1 in the resultant compound. But here there is no chemical reaction but only mixing of two metals to form an alloy known as sodium amalgam. Thus its oxidation number is unchanged and remains zero.
So, the correct answer is “Option D”.

Note: For oxidation number, a general procedure is to write down the final chemical formula of the compound and substitute the oxidation number of known elements forming the compound. Although the preparation of amalgam is exothermic there is no chemical reaction and thus no change in sodium oxidation number.