Question

Which of the following reacts most slowly with nitric acid?
A. Phosphorous
B. Chlorine
C. Sulphur
D. Iodine

Answer 1

The compound that will react most slowly with nitric acid should be an oxidising agent. Nitric acid itself is an oxidising agent, so when both oxidising agents react, the reaction should be slow.

Complete step by step solution:
In chemistry, an oxidizer (oxidant, oxidizer) could be a substance that has the power to provide oxygen or remove hydrogen from other substances. In other words they can just accept their electrons. Common oxidizing agents include oxygen, oxide and also halogens.
In one sense, an oxidiser could be a chemical species that undergoes a reaction during which it gains one or more electrons. In this sense, it's one component in an oxidation–reduction (redox) reaction. Speaking of the second sense, an oxidiser may be a chemical species that transfers electronegative atoms, usually oxygen, to a substrate. Common examples include Combustion, many explosives, and organic redox reactions which includes atom-transfer reactions.
On the other hand, Reducing agents are those elements or compounds that give away an electron to an electron deficient species in a redox chemical reaction. A reducing agent thus, gains oxygen when it loses electrons in the redox reaction. Reducing agents are meant to"reduce" oxidizing agents.
Now, nitric acid $HN{{O}_{3}}$ is a strong oxidising agent. That means it has a deficiency of electrons and can accept electrons from a suitable donor. But, chlorine is also an oxidising agent that needs electrons. So, when both of the species react, there is a deficiency of electrons that occur, and hence it is very hard to compensate for it. So the reaction proceeds very slowly.

So, in our case, the correct answer will be option B.

Note: As we know that if two oxidising agents react together, the reaction will be slow, the same is true if a reaction is carried out between two reducing agents. If nitric acid had reacted with phosphorus or iodine, which are reducing agents, the reaction would apparently have been faster.