Chemistry · Some Basic Concepts Of Chemistry · NEET
It means you try coefficients (the big numbers in front of formulas) one at a time, count the atoms, and keep adjusting until both sides have equal atoms of every element. There is no fixed formula; you just test values until it works. Start with the most complicated molecule and leave single elements like O2 or H2 for the end.
No. Never change a subscript. The subscript (the small number, like the 2 in H2O) is fixed because it defines the actual substance. If you change H2O to H2O2, you have written a completely different chemical (hydrogen peroxide, not water). You may only place or change coefficients, the big numbers in front.
A coefficient is the big number written in FRONT of a whole formula, like the 2 in 2H2O; it multiplies the entire molecule. A subscript is the small number written BELOW and INSIDE a formula, like the 2 in H2O; it counts atoms of one element in one molecule. In balancing you change coefficients only, never subscripts.
Balance metals and then non-metals first. Leave hydrogen and oxygen for last, because they usually appear in many compounds and get affected by other changes. A good rule: balance the element that appears in only one formula on each side first, and balance free elements (O2, H2, N2) at the very end.
Because of the Law of Conservation of Mass: atoms are neither created nor destroyed in a reaction. So the number of atoms of each element must be equal on the reactant side and the product side. An unbalanced equation would break this law and give wrong answers in NEET stoichiometry problems.
First finish balancing using the fraction if it helps. Then multiply EVERY coefficient in the whole equation by the denominator to clear the fraction. For example, if you get C4H10 + 13/2 O2, multiply all coefficients by 2 to get 2C4H10 + 13O2. Final answers should normally use the smallest whole numbers.
Make a small table. List every element and count its atoms on the left, then on the right. If every element matches and all coefficients are the smallest possible whole numbers, it is balanced. Also check the total charge is equal on both sides for ionic equations.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
For NEET-level equations, trial and error (hit-and-trial) is the standard and fastest method. There is also the algebraic method and the oxidation-number method for redox reactions, but simple molecular equations are almost always balanced by inspection.
The final answer should be the smallest set of whole numbers. You may use a fraction during the working (like 13/2 O2), but at the end multiply through to remove any fraction.
No. Balancing only ensures equal atoms on both sides, which follows the Law of Conservation of Mass. Total mass of reactants always equals total mass of products.
Almost every mole and stoichiometry question uses coefficients from a balanced equation to find mole ratios, limiting reagent, or mass of product. A wrong coefficient gives a wrong final numeric answer.
