What exactly is a redox reaction?

Question

My book explains: In redox reactions, the key chemical event is the net movement of electrons from one reactant ot the other.

What I am thinking is duh! Aren’t all reactions like this? What makes redox reactions different from any other reaction? Am I missing something here?

If there is a difference, can you give me an example to clarify this?

Answer 1

Not all rxns have electrons move.

Look at a metathesis reaction.

Say Pb(NO3)2 + 2NaCl ---> PbCl2 (ppt) + 2 HNO3 (aq)

Note that each of the reactants keeps it's orignal oxidation state. The atoms (or molecular ions) change partners but electrons "stay put". That's not exactly so, they do now get involved w/ other bonds, but for bookkeeping, the electrons stay about the original atom.

Many rxns are redox (combustion is a common one), but many aren't. The distinction is pretty important.

Answer 2

Sure. What they mean by "movement of electrons from one reactant to the other" is that the atom changes oxidation states. Like, it goes from a Fe+2 ion to a Fe+3 ion. Most of the heavier elements like transition metals can have variable oxidation states.

A regular reaction would be like:

Fe(OH)2 + MgCl2 --> FeCl2 + Mg(OH)2

The electrons move, but the atoms don't change oxidation states. The iron stays as a +2 ion the entire time.

An example of a simple redox reaction would be:

H2 + F2 --> 2HF

Notice that the hydrogen goes from a 0 state to a +1 state, and the fluorine goes from a 0 to a -1 state

Hope this helped.

Answer 3

Redox reactions are reactions where some of the atoms involved in the reaction change their oxidation numbers.

For example:

CH4 (g) + O2 (g) --> CO2 (g) + H2O

The left O2 changes oxidation number from 0 to -2 in the CO2 on the right side.
The C in CH4 changes from -4 to +4 in the CO2.

A reaction like this:

HNO3 + NaOH ---> NaNO3 + H2O

does not involve changes in the oxidation number of the atoms.
So it is not a redox reaction.

Answer 4

Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed.

This can be a simple redox process, such as the oxidation of carbon to yield carbon dioxide, it could be the reduction of carbon by hydrogen to yield methane (CH4), or it could be the oxidation of sugar in the human body, through a series of very complex electron transfer processes.

The term redox comes from the two concepts of reduction and oxidation. It can be explained in simple terms:

Oxidation describes the loss of an electron by a molecule, atom or ion
Reduction describes the gain of an electron by a molecule, atom or ion
Oxidation and reduction properly refer to a change in oxidation number — the actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. In practice, the transfer of electrons will always cause a change in oxidation number, but there are many reactions which are classed as "redox", though no electrons are transferred (such as those involving covalent bonds).
EX:iron(II) oxidizes to iron(III):
Fe2+ → Fe3+ + e-
hydrogen peroxide reduces to hydroxide in the presence of an acid:
H2O2 + 2 e- → 2 OH-
overall equation for the above:

2Fe2+ + H2O2 + 2H+ → 2Fe3+ + 2H2O
2.denitrification, nitrate reduces to nitrogen in the presence of an acid:
2NO3- + 10e- + 12 H+ → N2 + 6H2O
3.iron oxidizes to iron(III) oxide and oxygen is reduced forming iron(III) oxide (commonly known as rusting or tarnishing):
4Fe + 3O2 → 2 Fe2O3.

Answer 5

redox are reduction and oxidation at the same time. a reduction reaction involves a gain in electrons such as copper (III) going to copper (II). the copper has gained an electron and so has been made less positive.

an oxidation reaction is a loss of electrons, such as copper (II) going to copper (III).

in a redox reaction, one reactant goes through oxidation and gives an electron to the other reactant that goes through reduction.

i remember it by OIL RIG - oxidation is loss, reduction is gain.(in electrons).

so its a transfer of electrons from one reactant to the other .

Answer 6

Without too much confusion.

(RED)
Reduction is the GAIN of electrons.
(Ger, Gain Electrons Reduction)

(OX)
Oxidation is the LOSS of electrons.
(Leo, Loss Electrons Oxidation)

Don't quote me on this but i think this mainly happens in reactions involving IONs

Answer 7

a redox reaction is a reaction where one reactant gets oxidised and other reactant gets reduced simultaneously