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# Writing Chemical Equations

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 Sub Topics Chemical changes undergo changes both from physical as well as chemical characteristics. Shape, colour and state changes once a chemical change has gone through. These changes needs to be expressed in a systematic manner to make it more approachable for everyone.  Chemical changes wherever and whenever takes place takes into account the electronic configuration of reactants and means and methods to reach their respective octets. In order to maintain the systematic approach, the reactants and finished products are written in a specific way. These are maintained with proper numbers and symbols to make it reliable. Representations are known as chemical equations.

## Chemical Equations

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Chemical equations are specific representations of reactants and products both from numbers as well as symbols. The balancing part is taken up from both physical state as well as the number of moles that goes into reaction. The mole numbers are given out with specific requirements like precipitates and gaseous outcomes.

Chemical equations not only gives the reactants and products but also the physical state these substances are in and what kind of reaction it has gone through. The only thing a chemical equation would not provide is the rate of reaction.

### Conservation of Mass and Energy

Any chemical reaction that takes place is not accepted as complete unless the chemical balance is carried out. The balancing is basically done to provide the number of atoms that participate in the chemical change as well as moles of ions specific numbers that finally complete the products on the other side. This is done to understand how much of atoms are formed on the product side and whether or not these have same mass numbers as on the reactant side.

The balancing of chemical reaction gives us ample idea of the conservation of mass numbers on either side. The combinations might change but the overall numbers of atoms on either side of the reaction remains exactly the same.

2H2 + O2 $\rightarrow$ 2H2

By checking the number of atoms on either side we can see that number of hydrogen and Oxygen atoms on either side are same. The mass numbers if calculated shows the same values on either side. Hydrogen on either side has mass number of 4, while Oxygen has mass number of 32. The combination has changed though.

The energy which involves during any chemical change undergoes similar changes. Bonds are broken and then bonded into new combination. Each breaking of bonds gives off energy and bond formation requires energy and the resultant value at the end of reaction shows the same value on either side.

## Chemical Balance

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Chemical balance is carried out for various purposes. Whether we are trying to calculate the mole concept related values or identifying the number of atoms on either side of reaction or the manner in which these combinations have actually taken place shows exact values of moles and particle numbers.

Any change in number or mismatch gives an indication that the number of participating atoms on either side of reaction is not same and needs a relook. We can figure out the exact numbers of each participating atoms by doing a perfect chemical balance. These not help in identifying the ionic particles that has undergone change but also the final combinations which helps in figuring out the physical state of substances. In cases where the balancing is not done properly, the participating atoms might end up showing wrong products and their physical states.

Balancing of chemical equation is basically math. The participating atoms needs to be counted on either side and made equal. There are some basic rules which we need to follow to count the atoms and once that is done either side, all we need is to close the numbers on either side.

### Balanced Chemical Equation

Let us take the synthesis of ammonia.

N2 + H2 $\rightarrow$ NH3

The above chemical equation without the atoms is termed as skeletal equation. We can see that the number of nitrogen and hydrogen does not match with the number of atoms present in ammonia.

N2 + 3H2 $\rightarrow$ 2NH3

The diatomic form nitrogen is taken care of on product side and ammonia is provided with mole number of 2. The nitrogen on either side gets balanced but the hydrogen count changes. To tackle the changed number in hydrogen atoms on either side, we need to balance the atoms with a mole number of 3.

## Half Reaction Equation

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There are various types of reactions and for each of these forms we have specific representations. Every chemical change undergoes redox reactions. The participating atoms either undergo oxidation or reduction and the combined effect is given out as redox or reduction – oxidation.

Half reactions are basically reaction component of these redox reactions. These reactions provide ample information on whether an atom is undergoing oxidation or is getting reduced. These representations are done individually. So either the reduction is shown a specific participant or the oxidation state.

Cu2+ + 2 e- $\rightarrow$ Cu

Copper ion is gaining electrons to become reduced.

Zn (s) - 2e- $\rightarrow$ Zn2+

The zinc atom is losing electrons to get oxidised.

## Chemical Reaction Equations

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When we explain a chemical reaction it is always better to represent the same with chemical equation. These chemical equations not only help represent the specific number of atoms which participate in reaction but also to figure out whether or not a chemical change has given out gaseous products or precipitated.

Al2(SO4)3 + NaOH $\rightarrow$ Al(OH)3 + Na2SO4

The above reaction on one hand shows the chemical representation of the change that has taken place and on other hand also gives out the category of reaction. This reaction is double displacement reaction.

The balancing is done to figure out the final count of participating atoms.

Al2(SO4)3 + 6aOH $\rightarrow$ 2Al(OH)3 + 3Na2SO4

The representation shows the formation of hydroxide of aluminium and sodium salt of sulphate.