How to balance a chemical equation using redox reactions? PLease give me full explaination.

Asked by Prag Sangha | 9th Dec, 2013, 03:35: PM

Expert Answer:

(a) The steps to balance a chemical equation using redox reactions are as follows:

(*Note: All the steps are same in both the acidic and basic medium however only one difference is done that in acidic medium, H+ ions are used while in basic medium OH- ions are used.)

Step 1:

Write the correct formula for each reactant and product.

Step 2:

 Identify atoms which undergo change in oxidation number in the reaction by assigning the oxidation number to all elements in the reaction.

Step 3:

Calculate the increase or decrease in the oxidation number per atom and for the entire molecule/ion in which it occurs. If these are not equal then multiply by suitable coefficients so that these become equal.

Step 4:

Ascertain the involvement of ions if the reaction is taking place in water, add H+ or OH- ions to the expression on the appropriate side so that the total ionic charges of reactants and products are equal. Use, H+ ions when reaction in acidic medium and OH- ions when reaction in basic medium.

Step 5:

Equalize the number of H-atoms on both the sides by adding H2O molecules to reactants or product wherever necessary and also check the no. of oxygen atom and balance it.

For example: In acidic medium reaction: Cr 2 O 7 2- + NO 2 - → Cr 3+ + NO 3 - (acid)

=> The oxidation number is assigned as:


Answered by Hanisha Vyas | 10th Dec, 2013, 11:42: AM

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