超趕~~~chem CE MC Qs~~

The answer is C.

A incorrect.
Less reactive copper cannot displace more reactive iron from iron(II) nitrate solution.
For your question, nitrate ion cannot be an oxidizing agent unless in acidic solution. In such a case, the oxidizing agent is nitric acid, but not nitrate ion alone.
On the other hand, copper can be an reducing agent, but its reducing power is not high enough to reduce iron(II) ion, because copper is a weaker reducing agent than iron.

B is incorrect.
Less reactive bromine cannot displace more reactive chlorine from potassium chloride solution.
For your question, I- ion can be an oxidizing agent, but there is no I- ion at all.
On the other hand, Br2 can be an oxidizing agent, but its oxidizing power is not high enough to oxidize chloride ion, because bromine is a weaker oxidizing agent than chlorine.

C is correct.
More reactive iron can displace less reactive silver from silver nitrate solution.
Fe(s) + 2Ag+(aq) → Fe2+(aq) + 2Ag(s)
Fe is oxidized, as the oxidation number of Fe increases from 0 to +2.
Ag+ is reduced, as the oxidation number of Ag decrease from +1 to 0.

D is incorrect.
A precipitate of AgCl is formed. The precipitate is not redox as there is no change in oxidation number.
Ag+(aq) + Cl-(aq) → AgCl(s)
For your question, For your question, nitrate ion cannot be an oxidizing agent unless in acidic solution. In such a case, the oxidizing agent is nitric acid, but not nitrate ion alone.
On the other hand, Cl- ion is a very weak reducing agent, which can only be oxidized by very strong oxidizing agent, i.e. acidified potassium permanganate.

The answers for your questions are not related to the temperature.