Why the necessity of the partial equation method?......
Answers
☛ In order to balance simple chemical equations Hit and Trail method is the best ,but for complex equations this method is not so effective.since the different elements appear several times in a complex equations,it's balancing takes much time.It is also not clear how the reaction took place.
☛ It is because of these drawback of the Hit and Trail method that partial equation method is needed to balance.
☛ Partial equation methods : This method is used in balancing complex equations.Here the main reaction is presented in several simple steps .Then all the simple reactions are balanced by hit and trail method and added.Thus the balancing of equations becomes easy.
Now we will try to explain the methods with the help of example,
When carbon is heated with conc .Nitrate acid it gives carbon dioxide and Nitrogen dioxide.
The skeleton equation of the reaction is
C + HNO3 → NO2 + CO2 + H2O
This reaction take place in two steps
- In the first step,HNO3 is decomposed in NO2 ,H2O and nascent oxygen.
- In the second steps, nascent oxygen reacts with carbon and form carbon dioxide.
Now the first equation is multiplied by 2 and then added to get a complete balanced equation.
〚 2HNO3 → 2NO2 + H2O +'O'〛× 2
☛ C + 2 'O' → CO2
☛ C + 4HNO3 → 4NO2 + CO2 + 2H2O
In Partial equation method, the overall reaction is assumed to take place through two or more simpler reactions, which can be represented by partial equations. The steps are:
The given chemical equation is split into two or more partial equations.
Each partial equation is separately balanced by the hit and trial method.
These balanced partial equations are multiplied with suitable coefficients in order to exactly cancel out those common substances which do not appear in the overall chemical equations.
The balanced partial equations so obtained, are added to arrive at the balanced chemical equation
BALANCING OF CHEMICAL EQUATION BY PARTIAL EQUATION METHOD - DEFINITION
When equations contain many reactants and products they cannot be balanced by the hit and trial method. They are then balanced by the partial equation method. In this method the overall reaction is assumed to take place through two or more simpler reactions, which can be represented by partial equations. The steps involved are:
The given chemical equation is split into two or more partial equations.
Each partial equation is separately balanced by the hit and trial method.
These balanced partial equations are multiplied with suitable coefficients in order to exactly cancel out those common substances which do not appear in the overall chemical equations.
The balanced partial equations so obtained, are added to arrive at the balanced chemical equation