Oxidation, Reduction and Redox equations

What is oxidation?

The loss of electrons

What is reduction?

The gain of electrons

What is an oxidising agent?

Species that gains electrons

Define oxidation state.

A number which represents the number of electrons lost or gained by an atom of that element in the compound.

What is the oxidation state of oxygen in OF2 ?

What is the oxidation state of hydrogen in KH ?

What is the oxidation state of chlorine in NaClO ?

Define the term disproportionation?

Where in a redox reaction, the oxidation states of atoms of the same element, increase for some atoms, whereas decrease for some atoms.

What is the oxidation state of phosphorus in PCl5 ?

[P] = +5

What is the oxidation state of nitrogen in ammonia?

[N] = -3

(As ammonia is NH3 )

What is the oxidation state of arsenic in AsO4-3 ?

[As] = +5

What is the oxidation state of iron in K4 Fe(CN)6 ?

[Fe] = +2

Why is 1s22s22p5 a weaker reducing agent than 1s22s2 2p63s23p64s2 ?

The 2p electron is closer to the nucleus (smaller atom) than the 4s electron. Hence the nuclear attraction is stronger so the 2p electron is lost less easily than the 4s electron.

What happens in a redox reaction

Electrons are transferred from one species (element) to another.

● One element is oxidised whilst another is reduced

Why is, 2CrO4 2- + 2H+ → Cr2 O7 2- + H2 O, not a redox reaction?

Chromium and hydrogen have the same oxidation state (no element is reduced and oxidised).