How to determine reducing agent?

It is easy to determine if a chemical is reducing or not by simply noting the oxidation number before and after the reaction. For a reducing agent, it would be oxidized. So, the O.N. of it would be increased.


1. K+ is not a strong reducing agent!! While K is!!
K+ is weakly oxidizing since there nearly no chemicals that can reduce K+ to K.

K can reduce many non-metals or metals to the lowest oxidation number, if the condition is feasible.

K2Cr2O7 is a strong oxidizing agent as K+ does not do any works. The reacting species is Cr2O7^2-!!

2. Determine Br for what???

Determine if Br is reducing or oxidizing? right?

If it is Br2, it can be an oxidizing agent or reducing agent.
For Br-, it can only be reducing agent. eg. reduce Cl2 to Cl-

For Br2, being an oxidizing agent, eg. oxidize I- to I2.
being an reducing agent, reduce MnO4- to Mn2+ in acidic condition.

3. Being stable is relative. The can oxidize other chemical by gaining electrons. So the O.N. of them decrease!!

They become Cl-, Br- and O2-.

Reducing agent is the substance which is oxidized during a chemical reaction. So, you can use methods like oxidation numbers to find whether the substance is oxidized or not.

Q1) In most cases, K2Cr2O7 is oxidized ( Cr --> Cr3+). So it is usually reducing agent.
Q2)When Br2 --> 2Br-, it acts as oxidizing agent; When 2Br- --> Br2, it acts as reducing agent.
Q3)Oxidizing agent is determined by the behavior during chemical reaction. As Cl2, Br2 and O2 will gain electrons during reaction, they are oxidizing agent.