Balancing Equations

Just repeat: “I know I can, I know I can!”

Balancing equations

Due to the conservation of matter, equations MUST be balanced!

Atoms cannot be created or destroyed! Thus, the atoms in the products must

equal the total atoms in the reactantsREMEMBER: The atoms are only being

rearranged!

Coefficients vs. Subscripts

Subscripts tell us how many atoms there are in the molecule.

O2 This tells us that there are 2 Oxygen atoms

bonded to each other: O=OCoefficients tell us how many

molecules there are.

2O2

This tells us that there are 2 molecules of O2 O=O and O=O

How to balance an equation

Write out the equation with the reactants and products formulas

MgO + HBr ---> MgBr2 + H2O

Magnesium oxide and Hydrogen Bromide becomes Magnesium Bromide and Water.

How to balance an equation

Count the Atoms of each element on both sides of the equation.

MgO + HBr ---> MgBr2 + H2O

1 Mg 1 Mg1 O 1 O1 H 2 H1 Br 2 Br

How to balance an equation

Use coefficients to balance the equation

MgO + HBr ---> MgBr2 + H2O

We need a total of two hydrogen and bromine on the reactants side in order to balance this equation.

How to balance an equation

Finally…. Our balanced equation

MgO + 2HBr ---> MgBr2 + H2O

Double check your work, by counting again:1 Mg 1 Mg1 O 1 O2 H 2 H2 Br 2 Br

Try one on your own!

H + O H2O

H- 1 H- 2O- 1 O- 1

2H + O H2O

Let’s do another, for fun!!

Fe + HCl ---> FeCl2 +H2

1 Fe 1 Fe1 H 2 H1 Cl 2 Cl

Fe + 2HCl ---> FeCl2 +H2

Let’s try a couple more…N2 + O2 ---> N2O5

2 N 2 N2 O 5 O

We need to balance out the Oxygen first, then the Nitrogen. This gives us…

2N2 + 5O2 ---> 2N2O5

4 N 4 N10 O 10 O

One More…

C2H4 + O2 ---> CO2 + H2O

2 C 1 C4 H 2 H

2 O 3 O

C2H4 + 3O2 ---> 2CO2 + 2H2O