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Chemistry : Balancing Chemical Equations

 
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How to Balance a Chemical Equation?

A chemical equation must be balanced in accordance with the Law of Conservation of Matter. The Law states that matter is neither created nor destroyed during the chemical change that occurs in a chemical reaction. So, the total mass of reactants must equal the total mass of products in a balanced chemical equation.

In a balanced chemical equation, the number of atoms of each element in the reactants equals the number of atoms of each element in the products, since atoms are neither created nor destroyed.

Example:

Word Equation :
Ferric sulfate + Water + Sulfur dioxide → Ferrous sulfate + Sulfuric acid
Molecular Equation :
___ Fe2(SO4)3 + ___ H2O + ___ SO2 → ___ FeSO4 + ___ H2SO4
No of atoms : 2 Fe , 4 S , 2 H, 15 O → 1 Fe , 2 S, 2 H, 8 O

Balance Fe atoms : ___ Fe2(SO4)3 + ___ H2O + ___ SO2 → 2 FeSO4 + ___ H2SO4
No of atoms : 2 Fe , 4 S , 2 H, 15 O → 2 Fe , 3 S, 2 H, 12 O

Balance S atoms : ___ Fe2(SO4)3 + ___ H2O + ___ SO2 → 2 FeSO4 + 2 H2SO4
No of atoms : 2 Fe , 4 S , 2 H, 15 O → 2 Fe , 4 S, 4 H, 16 O

Balance H atoms : ___ Fe2(SO4)3 + 2 H2O + ___ SO2 → 2 FeSO4 + 2 H2SO4
No of atoms : 2 Fe , 4 S , 4 H, 16 O → 2 Fe , 4 S, 4 H, 16 O

Balanced Equation : Fe2(SO4)3 + 2 H2O + SO2 → 2 FeSO4 + 2 H2SO4
Thus, the stoichiometric coefficients in the balanced equation are
1 [for Fe2(SO4)3], 2 [for H2O], 1 [for SO2], 2 [for FeSO4] and 2 [for H2SO4].

Question : What numbers (stoichiometric coefficients) fill the blanks in the balanced molecular equation?
Answer : 1,2,1,2,2.


Practice Exercise for Chemistry Module on Balancing Chemical Equations


Practice Exercise for Chemistry Module on Balanced Chemical Equations from Word Equations
 
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