Chemistry

What is Partial method of balancing chemacal equations?

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2012-04-12 15:42:02

PARTIAL EQUATION METHOD:-----

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:

Steps and problem

* 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.

PROBLEM

Balance the equation,

NaOH + Cl2---------------------------------> NaCl + NaClO3 +

H2O

by partial equation method.

SOLUTION

The given skeleton equation can be split into two partial

equations.

Partial eq.1

NaOH + Cl2---------------------------------> NaCl + NaClO +

H2O

Partial eq.2

NaOCl ------------------------------> NaCl + NaClO3

The two partial equations are balanced by hit and trial

method.

Balanced partial eq.1

2NaOH + Cl2---------------------------------> NaCl + NaClO +

H2O

Balanced partial eq.2

3NaOCl ---------------------------------> 2NaCl + NaClO3

NaClO does not appear in the overall equation and so to cancel

it, the partial balanced equation 1 is multiplied by 3 and the two

equations are added to get the overall balanced equation.

2 NaOH + Cl2---------------------------------> NaCl + NaClO +

H2O * 3

3NaOCl ---------------------------------> 2NaCl + NaClO3

FINALLY

6NaOH + 3 Cl2---------------------------------> 5NaCl +

NaClO3 + 3H2O


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