Balanced Chemical Equation

 

Balanced chemical equations

 

According  to law of conservation of mass that mass can neither be created nor destroyed in a chemical reaction. It means to say that the total mass of the elements in the products side  of a chemical reaction to be equal to the total mass of the elements in the reactants side.

    Here , the total number of atoms of each elements remains same before and after a chemical reaction.

 

Example :--

 Zinc + Sulphuric acid      ➡       Zinc sulphate + Hydrogen

Zn + H2SO4  →  ZnSO4      +H2

 

Elements     number of atoms in reactants (LHS)

Zn                   1

H                     2

S                     1

O                     4

 

Elements     number of atoms in products (RHS)

Zn                   1

H                     2

S                     1

O                     4

 

 

 

 

Balance chemical equation :--

                                                The number of atoms of each elements are  the same on both sides of the arrow is known as balanced chemical equation.

There are following steps to write the balanced chemical equation :--

Step1:--  write the given equation to balance the chemical equation with the help of chemical formulae.

Fe + H2O   →         Fe3O4  +  H2

 

Step 2:--  write the number of atoms of each elements present in the unbalanced equation.

We write each side of the equation.  It means that the total number of atoms present in each elements on the products and reactants side must be compared.

Fe + H2O     →             Fe3O4  +  H2

 Here ,

In left side, the number of atoms of element in reactants (LHS):--

 

1 Fe (Iron)

2 H (hydrogen)

1 O (Oxygen)

 

In Right side, the number of atoms of element in Products (RHS):--

 

3 Fe (Iron)

2 H (Hydrogen)

4 O (Oxygen)

Step3:--  to write the balanced chemical equation , the reactants put on the left hand  side (LHS) and the products are to write on the right hand sided (RHS).

Now, the stoichiometric coefficients are added to molecules containing an element that has a different number of atoms in the reactant and products.

 Here coefficients mean the number in front of the chemical formula and coefficient indicates the mole of the compound. And subscripts mean the number below the atom that indicates the number of atom in a single molecule.

Here, the coefficient must balance the numbers of atoms on each side.

to calculate the number of atoms , multiply the coefficient and subscripts. And the number of atoms of the elements on both the reactants and products side must be added and updated.

To balance the above equation , let us start with the compound with msximum number of atoms , we select Fe3O4  . and in this compound the maximum number of the atoms  are oxygen. Here , there are four oxygen atoms on the RHS and only one atoms on LHS.

To balance the oxygen atoms:--

Atoms of oxygen           in reactant       in products

   Initial                         1 (in H2O)                  4(in Fe3O4)

To balance                       1*4                               4

 

To equalise the number of atoms , it must be noted that we cannot alter the formulae of the compounds or elements involved in the chemical reactions. For example :-- to balance the oxygen atoms , we can put coefficient “4” as 4H2O and not H2O4 or (H2O)4.

The partly balanced equation becomes :--

Fe + 4H2O    →      Fe3O4   +  H2   (partly balanced)

 

 

 

Step4:--

Step 3 is repeated until the number of atoms on both side reactants and products becomes equal. Let us balance the hydrogen atoms in the partly balanced equation.

 

To equalise the number of hydrogen H atoms , make the number of molecules of hydrogen as four on the RHS.

Atoms of hydrogen    in reactants          in products

Initial                         8 (in 4 H2O)          2(in H2)

To balance                8                         2*4

 

The equation will be :--

 

Fe + 4 * H2O →  Fe3O4 + 4H2  (this is partly balanced equation)

 

 

Step5:--

        Now the above equation is found partly balanced, we find the only one element is left to be balanced that is IRON (Fe)

Atoms of iron Fe     in reactants          in products

Initial                    1 (in Fe)                   3 (in Fe3O4)

To balance           1*3                                3

 

The equation will be :--

 3 Fe  + 4 H2O   →        Fe3O4    +  4H2

 

 

Step 6:-- now we check the correctness of the balanced equation. Count the atom of each elements on both side of the equation.

 3 Fe +4 H2O   →    Fe3O4    +  4H2   (balanced equation)

 

The number of atoms are equal on both sides. This equation is balanced equation. This method of balancing chemical equations is called as hit and trial method as we make trials to balance the equation by using the smallest whole number coefficient.

 

Step 7:--  writing symbols of physical state.

    The physical states of the reactants and products are mentioned along with their chemical formulae. This makes the balanced equation is more effective and informative. The phases of the reactants and products are mentioned using the symbols are such as

Gaseous ---- g

Liquid -----    l

Solid ----------- s

Aqueous ---- aq

Noted that the aqueous (aq) is written if the reactants or products is present as solution in water.

 

The balanced equation is represented as :--

 

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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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