Question

Nitric Acid does not react with:
a.) Silver
b.) Copper
c.) Zinc
d.) Gold

Answer 1

Hint: For this question, we need to consider electrochemical series as the key. The metals that come below hydrogen in the electrochemical series usually are very less reactive metals. That is why they cannot replace hydrogen and hence do not usually react with nitric acid, while the ones above hydrogen react with nitric acid very efficiently. This is the general concept.

Complete step-by-step answer:
According to the given question, we can find only zinc above hydrogen in the electrochemical series, while we can find silver and copper below hydrogen in the electrochemical series. This denotes that zinc is highly reactive in nitric acid while copper and silver are less reactive in Nitric acid. On the other hand, gold being a noble metal, does not react at all with nitric acid. The reactions for silver, copper, zinc in Nitric acid are given below:

Reaction with silver –
$\text{Ag(s) + 2HN}{{\text{O}}_{\text{3}}}\text{(aq) }\xrightarrow{{}}\text{ AgN}{{\text{O}}_{\text{3}}}\text{(aq) + }{{\text{H}}_{\text{2}}}\text{O(l) + N}{{\text{O}}_{\text{2}}}\text{(g)}$
Reaction with copper –
$\text{Cu(s) + 4HN}{{\text{O}}_{\text{3}}}\text{(aq) }\xrightarrow{{}}\text{ Cu(N}{{\text{O}}_{\text{3}}}{{\text{)}}_{2}}\text{(aq) + 2}{{\text{H}}_{\text{2}}}\text{O(l) + 2N}{{\text{O}}_{\text{2}}}\text{(g)}$
Reaction with zinc –
$\text{5Zn(s) + 12HN}{{\text{O}}_{\text{3}}}\text{(aq) }\xrightarrow{{}}\text{ 5Zn(N}{{\text{O}}_{\text{3}}}{{\text{)}}_{2}}\text{(aq) + 6}{{\text{H}}_{\text{2}}}\text{O(l) + }{{\text{N}}_{\text{2}}}\text{(g)}$

When nitric acid reacts with silver, silver nitrate is formed along with water and oxides of nitrogen. The by-products of this reaction depend upon the concentration of nitric acid that is used.

When concentrated nitric acid reacts with copper, copper gets oxidized and produces ${\text{C}}{{\text{u}}^{{\text{2 + }}}}$ions. Nitric acid is then reduced to nitrogen dioxide which is a poisonous brown gas with an irritating odour.

When zinc reacts with dilute nitric acid, zinc nitrate is formed along with hydrogen gas. These products are formed because of the reduction process which follows with the reaction of nitric acid by nascent hydrogen that is produced in increasing amounts as the concentration of nitric acid is lowered.

Nitric acid does not react with Gold.
Therefore, the correct answer is Option D.

Note: Though nitric acid cannot dissolve gold in it, aqua-regia is a mixture of nitric acid and hydrochloric acid in the ratio of 1:3, that is one part of nitric acid in three parts of hydrochloric acid which dissolves gold and any noble metal efficiently. Gold is also sometimes referred to as the royal metal and aqua-regia in Latin means royal water.