balancing chemical reations class notes

BALANCING CHEMICAL EQUATIONS
STEP 1 Write the Chemical Equation

Start by writing the chemical equation for the reaction to balance. A chemical equation shows the
reactants on the left side and the products on the right side, separated by an arrow. For example,
let's consider the reaction between hydrogen gas (H₂) and oxygen gas (O₂) to produce water (H₂O):


H₂ + O₂ → H₂O


STEP 2 Count the Number of Atoms on Each Side

Next, count the number of atoms of each element on both sides of the equation. This includes the
atoms in both the reactants and the products. Make a list of the atoms and their counts for each
element. For our example, we have:

H: 2 atoms on the left side, 2 atoms on the right side
O: 2 atoms on the left side, 1 atom on the right side


STEP 3 Choose an Element to Start Balancing

Select an element that appears in more than one molecule on either side of the equation. For
example, oxygen (O) is a good choice because it appears in two molecules on the left side and one
molecule on the right side.

H₂ + O₂ → 2H₂O


STEP 4 Add Coefficients

To balance the number of oxygen atoms, add a coefficient (a number in front of the molecule) to the
molecule(s) that contain the element. The coefficient multiplies the number of atoms in that molecule.
In our example, we can balance oxygen by adding a coefficient of 2 in front of the water molecule:

H₂ + O₂ → 2H₂O


STEP 5 Check the Balance

After adding the coefficient, check if the equation is balanced. Go back and count the atoms of
the element you just balanced and verify that they are now equal on both sides.

H: 2 atoms on the left side, 4 atoms on the right side
O: 2 atoms on the left side, 4 atom on the right side 1.