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1. Chemical Reactions and Equations : Balancing A Chemical Equation Science class 10th:English Medium NCERT Book Solutions
NCERT Books Subjects for class 10th Hindi Medium
1. Chemical Reactions and Equations
Balancing A Chemical Equation
Balancing a Chemical Equation.
Here we would learn the method how to balance a chemical reaction.0
The method which we apply e.i hit and trail or inspecting method. Here we take Equation Fe + H2O → Fe3O4 + H2 as example I:
Steps;
(i) Write each formula in box or imagine that each formula is in box. It is so that you have to mind no changes should be made inside the box.
(ii) Count and list the numbers of atom of different element that present in unbalanced equation. Like this
Elements Reactant Product
Fe 1 3
O 1 4
H 2 2
First observe that what element has the maximum number of atoms. It may be from reactant and from product. Using this criteria we find that Fe3O4 is that compound and element is O that have maximum 4 atoms.
To equalise the number of atoms of oxygen, we can put the coefficient 4 with H2O as 4H2O. Then we get the equation as,
Fe + 4H2O → Fe3O4 + H2
(iii) The next maximum number of atoms having Fe. Which can be equalised
by same process.
Putting the coefficient 3 with Fe as 3Fe in reactant side. Now, the equation will be
3Fe + 4H2O → Fe3O4 + H2
(iv) Finally we come to equalise Hydrogen atom of both side. We observe that 4H2 in reactant and H2 in product. Total atom of hydrogen in reactant side is 4 × 2 = 8 and 2 in product. Then,
Here we cannot put 2 on LHS and 8 on RHS. (8 ÷ 2 ) =4 , the coefficient will be 4 that equalises hydrogen atom on RHS. So finally equation will be.
3Fe + 4H2O → Fe3O4 + 4H2 (balanced equation)
Example II. We take,
HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O
Steps:
(i) On observing the above chemical equation we see NO3 has maximum number of atoms/molecules. To equalise it we have on LHS 1 molecule and on RHS 2 molecules. So
Here Nitrogen and oxygen have been balanced, then Equation will be;
2HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O
(ii) Next calcium is already balanced, now we have to balance only hydrogen atoms.
Product need 2 as coefficient because (4 ÷ 2) = 2 , then equation will be;
2HNO3 + Ca (OH)2 → Ca(NO3)2 +2H2O
(iii) On counting and listing the numbers of atom of different element that present in equation above.
Elements Reactant Product
O 8 8
N 2 2
Ca 1 1
H 4 4
Hence we get a balanced equation
2HNO3 + Ca (OH)2 → Ca(NO3)2 +2H2O
I think now you have learnt how to balance a skeletal equation.
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See other sub-topics of this chapter:
2. Writing A chemical equation
3. Balancing A Chemical Equation
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