A chemical equation is a written symbolic representation of an actual chemical reaction (The symbols are the elemental letter or letters representing that element). The reactant chemical(s) are given on the left-hand side and the product chemical(s) are given on the right-hand side. The two (reactant & product) are connected with an arrow leading from the left to the right, symbolizing the reaction. The law of conservation of mass states that no atoms can be created or destroyed in a chemical reaction, so the number of atoms that are present in the reactants has to balance the number of atoms that are present in the products. Follow this guide to learn how to Balance Chemical Equations differently.
Write down the given equation.
For this example, we will use:
PCl5 + H2O –> H3PO4 + HCl
Assign a letter to each substance.
- aPCl5 + bH2O –> cH3PO4 + dHCl
Check the number of each element found on both sides, and set those equal to each other.
- aPCl5 + bH2O –> cH3PO4 + dHCl
- On the left side, there are 2b atoms of hydrogen (2 for every molecule of H2O), while on the right side, there are 3c+d atoms of hydrogen (3 for every molecule of H3PO4 and 1 for every molecule of HCl). Since the number of atoms of hydrogen has to be equal on both sides, 2b must be equal to 3c+d.
- Do this for each element.
- P: a=c
- Cl: 5a=d
- H: 2b=3c+d
Solve this system of equations to get the numeric value for all the coefficients.
Since there are more variables than equations, there are multiple solutions. You must find the one where every variable is in its smallest, non-fractional form.
- To quickly do this, take one variable and assign a value to it. Let’s make a=1. Then start solving the system of equations to get the following values:
- Since P: a = c, we know that c = 1.
- Since Cl: 5a = d, we know that d = 5
- Since H: 2b = 3c + d, we can calculate b like this:
- 2b = 3(1) + 5
- 2b = 3 + 5
- 2b = 8
- b=4
- This shows us the values are as follows:
- a = 1
- b = 4
- c = 1
- d = 5
This is called Algebraic Balance
more methods coming soon…