Chemistry is, if you ask people, most easily scoring subject that you will find in JEE. And especially if you are able to master physical chemistry then you can expect your path to be fairly easy. All you need to do is be thorough with the concepts involved and solving problems will be cakewalk. To help you with your preparations, here, we will focus on the topic redox reactions, which is one of the first few topics taught in physical chemistry and understanding these topics will help you with other topics in physical chemistry as well as organic and inorganic chemistry.
So, redox reaction is defined as a reaction in which both oxidation and reduction takes place simultaneously. These reactions involve exchange of electrons and ions between the reacting elements leading to the formation of new compounds and ions. For identifying whether a reaction is redox or not you need to understand the terms oxidation and reduction appropriately.
Oxidation & Oxidising Agent
Different to what has been taught during in 10th grade, oxidation is not limited to addition of oxygen or removal of hydrogen from an element or compound but rather any change which results in addition of electrons in an element/compound thereby increasing its valence state is called oxidation. The compound which aids oxidation is called oxidising agent.
Reduction & Reducing Agent
Reduction is complete opposite of oxidation i.e. reduction involves removal of electrons from an element/compound causing a decrease in its valence state. The compound which aids reduction is called reducing agent.
It is very important to note that an oxidising agent reduces itself leading to a decrease in its valence state and reducing agent oxidises itself causing an increase in its valence state.
Balancing Redox reactions
Because of the reason that redox reactions involve exchange of electrons and ions, balancing chemical equations representing a redox reaction need specific steps to be followed. There are two principal methods that can be used to achieve this and they are –
- Oxidation number method.
- Ion electrode or Half-reaction method.
Common oxidising and reducing agents
It is important that you remember the common oxidising and reducing agents as that will also help you in inorganic chemistry to guess the nature of reaction and predict the products that might form. Some of these are –
Law of Equivalence
This law states that the number of equivalents of reactants is equal to the number of equivalents of product. To get the equivalents of a compound we need to know its n-factor which can be found from the chemical equation of the reaction. Then using the given equation, we can find out the equivalents of a compound. Here, w is the weight of the compound, E and M1 are the equivalent mass and molar mass of the compound and n is the n-factor.
This a very important topic with questions asked quite often in exams. Questions asked generally will be based on concepts of mole fraction, mass fraction, molarity and similar concentration definitions, titration and back titration (N1V1 = N2V2). Solving these question demands ample practise beforehand so make sure you do that.
Apart from the aforementioned topics, questions may be based on finding strength of chemical compounds based on titration. These are questions based on a combination of ionic equilibrium & chemical equivalence.
Hope these points help you in your preparation of exams and as stressed always, make sure you have enough practise because that’s the key to crack any topic. You can gain some quick insight on co-ordination compounds here. Keep following Toppr for such tips and tricks.
As the exam season approaches all we wish is that May the force be with you!