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7 Steps To Balance Chemical Equations

Aug 24, 2022
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Key Concepts:

  • Chemical equation
  • Skeleton equation
  • Law of conservation of mass
  • Balanced chemical equation

Chemical Reaction: 

The chemical changes of two or more chemicals at a time are called chemical reactions. The chemical reaction can be represented by the equation. The word equation represents the chemical words and the initial substances and the final substances after the chemical reaction separated by the arrow mark 

Chemical Equation:  

Balance chemical equations is a symbolic representation of the reactants and products of a chemical reaction. The initial chemicals before the reaction are called the reactants, and the chemicals after the reaction are called the products. 

The number written in front of the chemical name is called the coefficient, and the number that is written after the chemical symbol in small is called the subscript. In the above chemical equation, the chemicals HCl and Na are called the reactants and the chemicals NaCl and H are the products. 

Skeleton Equation: 

Chemical equation with an unequal number of atoms present in the reactants side and products side is called a skeleton equation.  

Fe  +  O2    →    Fe2O3 

parallel

In the reactants part, we see there is only one iron atom and two oxygen atoms, but in the product part, we see there are two iron atoms and three oxygen atoms. The equation is not balanced. 

What is a balanced equation? 

Chemical equation with an equal number of atoms present in reactants side and products side is called a balanced equation. Balanced equation is also called a stoichiometric equation.  

Example: 

Take the example of the forming of the water molecule from the hydrogen and oxygen atoms. The equation is as follows: 

2H2 + O2     →     2H2

Law of conservation of mass: 

The law of conservation of mass needs to be kept in mind while doing the balancing of the equation. According to the law of conservation of mass, mass of reactants and products are to be equal, and balancing is done as per the law. According to the law of conservation of mass, mass can neither be created nor be destroyed but can be converted from one form to the other. 

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Characteristics of the balanced equation: 

Balanced equation gives the number of participating reactants and products exactly. Balanced equations possess substances in such a way that the total charge on the left hand and right hand is balanced. 

Stoichiometric coefficients: 

The number of times each reactant is reacting and the number of times each product is appearing in a balanced equation is said to be stoichiometric coefficients. 

Fig 1

In the above example, we have the coefficient for hydrogen as 2, and the coefficient for oxygen is 1. In the product section, the coefficient of the water molecule is 2. Two hydrogen atoms react with one oxygen molecule to get the two water molecules. 

How to balance equations? 

For balancing a chemical equation, we follow seven basic steps.  

Step 1: To balance a chemical equation, first draw boxes around each reactant and product and do not make any changes to it. 

Fe  +  H2O       →      Fe3O4  +  H2 

Step 2:  List the number of atoms of each element present in the unbalanced equation. 

Fig 2

Step 3: We should always choose a compound with a maximum number of atoms in it, either on reactants side or products side.  

Fe + H2O → Fe3O4 + H2 

Here we select Fe3O4 which contains 4 oxygen atoms on the right hand side. 

As we cannot make H2O to H2O4 in order to increase oxygen atoms, so we make it to 4H2O. 

Fe + 4H2O → Fe3O4 + H2 

Step 4:  Balance other atoms now like Fe and H.  

Fe + 4H2O → Fe3O4 + H2 

Atoms of H are 8 on L.H.S and 2 ON R.H.S, so multiply H2 on R.H.S with 4, so we get  

Fe + 4H2O  →  Fe3O4 + 4H2 

Step 5: Fe + 4H2O → Fe3O4 + 4H2 

Pick the last element Fe from the above partly balanced equation. Fe are 3 on R.H.S and 1 on L.H.S, so multiply 3 on L.H.S  

3Fe + 4H2O  →  Fe3O4 + 4H2 

Step 6:  

Check the equation whether it is balanced or not by counting the number of atoms on L.H.S and R.H.S  

3Fe + 4H2O  →  Fe3O4 + 4H2 

This is the balanced equation. 

Step 7:  Indicate the physical state of all the reactants and products by writing symbols in brackets as subscripts on the right corner below the formula.  

Symbols: 

The symbols are denoted with some letters. For solids, we use “s”, for liquids we use “l”, for gases we use “g”, for aqueous solutions we use “aq”.  These symbols help us to classify the type of equation. 

Balanced equation representation: 

Take the example of the chemical equation 

3Fe(s)  + 4H2O(l)   →  Fe3O4(s) + 4H2(g) 

This chemical equation is called the Heterogeneous chemical equation. It is called the Heterogeneous equation as reactants and products have different physical states. 

Balanced equations need not contain physical states unless it is necessary. Catalyst and reaction conditions like temperature and pressure are represented above and below the arrow in the equation.  

Summary

  • Chemical equation with an equal number of atoms on L.H.S and R.H.S is a balanced equation or stoichiometric equation.
  • Chemical equation with an unequal number of atoms on L.H.S and R.H.S is an unbalanced equation or non-stoichiometric equation or skeleton equation.
  • Balancing an equation can be done by following seven rules.

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