Question

When L is heated with iron metal, it forms a compound FeL. What chemical term would you use to describe the change undergone by L?

Answer 1

There are two types of changes that can be undergone by a species during a chemical reaction:
Oxidation: when a species loses or donates its electrons, it is said to have undergone oxidation.
Reduction: When a species gains electrons, it is said to have undergone reduction.
Electrons lost by one are gained by the other in a chemical reaction. It means if one species has undergone oxidation, the other will have to undergo reduction. Metals tend to donate electrons.

Complete step by step answer:
As said earlier, metal tends to donate electrons and it means that in a chemical reaction it is the metal atom which will undergo oxidation.
According to the question, L is heated with Fe and gives FeL:
${{Fe + L}}\xrightarrow{{{\Delta }}}{{FeL}}$
Now, since Fe has undergone oxidation, L is said to have undergone reduction.
Now, Fe (iron) can have oxidation states 2 and 3.
Since the reaction leads to the formation of FeL, it means that L has the same magnitude of oxidation state as iron but has an opposite sign.
Therefore, the oxidation state of L in FeL can be $- 2$ or $- 3$

Hence, the change undergone by L is the reduction reaction. It has changed to zero oxidation state to $- 2$ or $- 3$ oxidation state.

Note:
Reactions, where oxidation and reduction take place, are known as redox reactions.
It is important to know that in a reaction electrons are neither created nor destroyed, they remain constant.
Therefore, the number of electrons lost by species is equal to the number of electrons gained by the other.