Question

what is redox reaction ..with eg.

Answer 1

Another example of a redox reaction is the formation of hydrogen fluoride. We can break the reaction down to analyze the oxidation and reduction of reactants. The hydrogen is oxidized and loses two electrons, so each hydrogen becomes positive. The two electrons are gained by fluorine, which is reduced.In a redox reaction, one or more element becomes oxidized, and one or more element becomes reduced. Oxidation is the loss of electrons whereas reduction is the gain of electrons

Answer 2

Oxidation-Reduction or "redox" reactions occur when elements in a chemical reaction gain or lose electrons, causing an increase or decrease in oxidation numbers. The Half Equation Method is used to balance these reactions.

In a redox reaction, one or more element becomes oxidized, and one or more element becomes reduced. Oxidation is the loss of electrons whereas reduction is the gain of electrons. An easy way to remember this is to think of the charges: an element's charge is reduced if it gains electrons (an acronym to remember the difference is LEO = Lose Electron Oxidation & GER = Gain Electron Reduction). Redox reactions usually occur in one of two environments: acidic or basic. In order to balance redox equations, understandingoxidation states is necessary.
For example looking at the following reaction in an acidic solution 

MnO−4(aq)+I−(aq)→Mn2+(aq)+I2(s)