Do anyone know how to balance redox reactions?
Answers
Answer:
Redox Reactions
The reduction is the gain of electrons whereas oxidation is the loss of electrons. The combination of reduction and oxidation reaction together refers to redox reaction/redox process. As discussed, it is very important to understand “balancing redox reactions”.
There are generally two methods for balancing redox reactions (chemical equations) in a redox process. The two methods are- Oxidation Number Method & Half-Reaction Method.
Balancing Redox Reactions
Oxidation number method is based on the difference in oxidation number of oxidizing agent and the reducing agent. Half-reaction method depends on the division of the redox reactions into oxidation half and reduction half. It depends on the individual which method to choose and use.
Balancing Redox Reactions by Oxidation Number Method
As with every other reaction, it is very important to write the correct compositions and formulas. A very important thing to keep in mind while writing oxidation-reduction reactions is to correctly write the compositions and formulas of the substances and products present in the chemical reaction. The steps of the oxidation number method are as follows:
Step 1
Correctly write the formula for the reactants and the products of the chemical reaction.
Step 2
Determine correctly the atoms that undergo oxidation number change in the given reaction by allocating the oxidation number of the individual elements present in the reaction.
Step 3
Calculate the oxidation number on the basis of each atom for the given molecule or ion of the chemical reactions. If the numbers are not equal then multiply it to such a number that overall these numbers become equal. If in a case, two substances are either only oxidized or only reduced then this signifies that something is wrong with the chemical reaction. This signifies that either the formulas of the reactant or the products are incorrect. This can also mean that the allocation of oxidation numbers is incorrect.
Step 4
Keep in mind the involvement of the ions if the reaction occurs in water. Accordingly, add H+ or OH– ions in the appropriate side of the reaction. Overall, the ionic charges of reactant and products will be equal. However, if the reaction takes place in acidic solution then add H+ ions in the chemical equation. Similarly, if the reaction takes place in the basic solution add OH– ions in the chemical equation.
Step 5
It is very important to equate the number of hydrogen atoms on each side of the equation by adding water molecules or H2O molecules. Additionally, it is necessary to check the oxygen atoms present in the equation. It will be a balance reaction if there are equal numbers of oxygen atoms present in both the reactant as well as the product the side.
We will further understand the steps of balancing redox reactions by solving a problem on the basis of oxidation number method.
Balancing Redox Reactions by Half-Reaction Method
In this procedure, we split the equation into two halves. Thereafter, we balance both the parts of the reaction separately. Finally, we add them together to give a balanced equation. We will demonstrate this method with an example so as to understand the steps of balancing redox reactions by half-reaction method.
For instance, a reaction is given where Fe2+ ions are converted to Fe3+ ions by dichromate ions in an acidic solution. The dichromate ions (Cr2O72–) are reduced to Cr3+ ions in the reaction. We have to balance the above redox reaction.
Answer:
Guidelines for balancing redox equations
Step 1. Write down the unbalanced equation
Step 2. Separate the redox reaction into half-reactions
a) Assign oxidation numbers for each atom
b) Identify and write out all redox couples in reaction
c) Combine these redox couples into two half-reactions
Step 3. Balance the atoms in each half reaction
a) Balance all other atoms except H and O
b) Balance the oxygen atoms with H2O
c) Balance the hydrogen atoms with H+
d) In a basic medium, add one OH- to each side for every H+
Step 4. Balance the charge with e-
Step 5: Make electron gain equivalent to electron loss in the half-reactions
Step 6: Add the half-reactions together
Step 7: Simplify the equation
Finally, check that the elements and charges are balanced