[Even]

How do you determine what the products will be when one chemical gets reduced or oxidized.

I know the rule is reducing agent will decrease the number of oxygen of another species. Oxidizing agent increase the number of oxygen of another species. But WHY?

SO₃^2- in a solution will react with oxygen in air, giving SO₄^2-. Can anyone show me the eqaution and how it relates to redox reaction?

Thanks

[opti384]

You might want to go over the definition of reduction and oxidization again. Redox reactions are not just about oxygens. When an element in a compound loses an electron we say that it's oxidized and when it gains an electron we say that it's reduced (of course when an oxygen is gained the compound is oxidized and vice versa)

[Even]

of course when an oxygen is gained the compound is oxidized

I just dont understand this part

[opti384]

When we talk about redox, there are three definitions about it.

The first one is if a compound or an atom gains oxygen it is oxidized and if it loses oxygen it is reduced.

The second one is if a compound or an atom loses hydrogen it is oxidized and if it gains hydrogen it is reduced.

These two definitions are somewhat limited and more broader definition will be the third one which is

if a compound or an atom loses electron it is oxidized and vice versa.

[Professor 0110]

In general, an element that is reduced gains electrons during a chemical reaction and an element that is oxidized loses electrons. In all chemical reactions there is always oxidation and reduction happening. Basic ionic equations clearly demonstrate this principle.

For example:

K + NaC --> KCl + Na

In the above example, K is more reactive than Na and therefore displaces Na in solution. The K metal goes from being a metal to being an ion with a +1 charge. It has therefore lost an electron. It has therefore been oxidized. Na goes from being an ion with a +1 charge bonded to Cl to being just Na metal with no charge. It gains an electron (the one K lost) and is therefore reduced.

Do you see how it works? Further, Na is the oxidizing agent, since its reduction CAUSED K's oxidation. K is the reducing agent since K losing an electron to Na CAUSES Na's reduction (gain of electron).

Hope it makes more sense now.

[Even]

When we talk about redox, there are three definitions about it.

The first one is if a compound or an atom gains oxygen it is oxidized and if it loses oxygen it is reduced.

The second one is if a compound or an atom loses hydrogen it is oxidized and if it gains hydrogen it is reduced.

These two definitions are somewhat limited and more broader definition will be the third one which is

if a compound or an atom loses electron it is oxidized and vice versa.

Thanks, but I don't understand how the first definition relates to the third definition.

[Even]

In general, an element that is reduced gains electrons during a chemical reaction and an element that is oxidized loses electrons. In all chemical reactions there is always oxidation and reduction happening. Basic ionic equations clearly demonstrate this principle.

For example:

K + NaC --> KCl + Na

In the above example, K is more reactive than Na and therefore displaces Na in solution. The K metal goes from being a metal to being an ion with a +1 charge. It has therefore lost an electron. It has therefore been oxidized. Na goes from being an ion with a +1 charge bonded to Cl to being just Na metal with no charge. It gains an electron (the one K lost) and is therefore reduced.

Do you see how it works? Further, Na is the oxidizing agent, since its reduction CAUSED K's oxidation. K is the reducing agent since K losing an electron to Na CAUSES Na's reduction (gain of electron).

Hope it makes more sense now.

Thank you. I think I understand redox reaction in terms of electron transfer during a reaction, but I am not quite clear on how the number of oxygen changes during a redox reaction. I am trying to tie these 2 things together. (Number of Oxygen gain/lose, number of electron transferred)

[opti384]

The definition of electron gain/loss is broader than the others. Which means that in every redox reactions there must be electron gains or losses. Even though there are no oxygens and hydrogens involved in redox reactions, it doesn't mean that the reaction is not a redox reaction. In other words, in a redox reaction which entails oxygen gain/loss, still there is electron gain/loss.