Identifying different parts of a chemical equation

The different parts of a chemical reaction involve the reactants, the products, the co-efficients and the subscripts. The reactants are the elements or compounds with which we begin the reaction. The products are those which are formed after the reaction. Co-efficients are the numbers present before the reactants and products indicating the number of moles present. Subscripts on the other hand are the numbers placed on the bottom right of the reaction and indicate the number of atoms taking part in the reaction.

How to identify the reactants and products:
Identifying the reactants and the products are extremely easy. The elements or compounds present on the left side of the arrow are the reactants and the elements or compounds present on the right side of arrow are products. Reactants are the initial substances and so they are present on the left side. The products are formed as a result of the reaction and so they are present on the right hand side.

For example:
Na2CO3 + 2HCl → 2NaCl + H2CO3
In the above reaction the reactants are the Na2CO3 and HCl, while the products are NaCl and H2CO3.

How to identify the co-efficients:
To identify the co-efficients, we look at the number present before the elements. Then we look at the entire reaction and decide whether they are no. of molecules or no. of moles.

For example:
2N2 + 5O2 → 2N2O5
In the above reaction the co-efficient of oxygen is 5 while that of nitrogen is 2 and that of nitrogen pentoxide formed is 2. This means that 2 molecules of nitrogen react with 5 molecules of oxygen to form 2 molecules of nitrogen pentoxide.
To identify subscripts you look at the number represented in the subscript form included within the formula.

For example in the above reaction, the subscript of oxygen is 2 while its co-efficient is 5. 2 is the number subscripted after the element ‘O’, therefore it is the subscript while 5 is present before the element and is represented in the normal form so it is the co-efficient.

How to identify solid, liquid or gas:
To identify whether the elements are in liquid state or solid state or gaseous state we have to look for certain symbols.

Following are a few symbols and their meanings:
(s) – means solid
(l)-means liquid
(aq)-means aqueous which also means liquid
(g)-means gaseous state
For example:
MgCO3 (s) → MgO (s) + CO2 (g)

In the above reaction, magnesium carbonate and magnesium oxide are solid while carbon dioxide is in the gaseous state.