Chemistry · Redox Equilibrium · NEET
Oxidation means LOSING electrons. Use OIL: Oxidation Is Loss. When a species loses electrons, its oxidation number goes up (becomes more positive). Reduction is the opposite: RIG means Reduction Is Gain, so the oxidation number goes down.
OIL = Oxidation Is Loss (of electrons). RIG = Reduction Is Gain (of electrons). Read left to right: the first three letters O-I-L are oxidation, the next three R-I-G are reduction. This is the safest way for NEET to avoid mixing up the two.
Adding oxygen is only the old, narrow idea. The modern definition used in NEET is based on ELECTRON transfer, because it works for every redox reaction, even ones with no oxygen. Adding oxygen or removing hydrogen usually means the atom lost electrons anyway, so OIL RIG still holds.
Find the oxidation number of each element before and after the reaction. The atom whose oxidation number INCREASES lost electrons, so it was oxidised. The atom whose oxidation number DECREASES gained electrons, so it was reduced. In Zn + Cu2+ -> Zn2+ + Cu, Zn goes 0 -> +2 (loss, oxidised) and Cu goes +2 -> 0 (gain, reduced).
No, and this is a common NEET trap. The species that is oxidised (loses electrons) is the REDUCING AGENT, because it gives electrons to the other one. The species that is reduced (gains electrons) is the OXIDISING AGENT. In Zn + CuSO4, Zn is oxidised and acts as the reducing agent; Cu2+ is reduced and acts as the oxidising agent.
Yes. Electrons that one species loses must be gained by another. So oxidation and reduction always occur at the same time in a redox reaction. You can never have loss of electrons without something else gaining them.
Which reaction is NOT a redox reaction?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
OIL RIG is a memory aid, not something you write as the final answer. Use it to decide correctly, then justify with oxidation-number change or electron transfer, which is what NEET expects.
They mean the same thing. OIL RIG = Oxidation Is Loss, Reduction Is Gain. LEO GER = Lose Electrons Oxidation, Gain Electrons Reduction. Pick one and stick with it so you never get confused in the exam.
Yes. An increase in oxidation number means the atom lost electrons, which is oxidation (OIL). A decrease in oxidation number means gain of electrons, which is reduction (RIG).
Yes, in a disproportionation reaction one element in one oxidation state both loses and gains electrons at the same time, giving two different products. OIL RIG still applies to each part.
