Balancing Chemical Equations
Brittany Camp
&
David Mejia
Objective
• To be able to identify what is occurring in a
chemical reaction and to be able to balance
the equation between the reactors.
Background
• At NASA’s Spaceward Bound scientist are
trying to find if there is life on Mars.
• The Mojave Desert resembles the terrain on
Mars.
• The scientist run many different experiments
to find if there is life in the Mojave Desert.
Hypothesis
• If there is life in the soil in the Mojave Desert,
then there could be life in the soil on Mars.
Experiment
Scientist collected soil samples from the Mojave desert,
from many different locations.
Experiment Continued
The soil was labeled and put into test tubes.
The test tubes where then added a solution.
Experiment Continued
If there was life in the test tube then the solution would turn blue.
The more life there was the bluer it got.
Then it was measured by a spectrometer.
What is a Chemical Equation?
• When a chemical reaction occurs between
solutions it can be described by an equation.
• This shows the chemicals that react (called
reactants) on the left-hand side
• The two sides are separated by an arrow that
shows what is yielded from the reactants.
• The chemicals that are produce (called
products) on the right-hand side.
Concept
• Look at this chemical equation:
Al + O2
Al2O3
• Oxygen gas is diatomic, it is always in pairs.
• A molecule of aluminum oxide consists of two
aluminum atoms combined with three oxygen
atoms.
Balancing the Equation
• We can balance the equation by looking at what is
doesn’t make sense in the equation. We see first that
there are 2 Al on the right, so we add 2 to the left
2 Al + O2
Al2O3
• Now there are the same number of Al atoms, we see
that there is one more atom of O on the left, we must
find a common factor of 6 on each side by adding 3 on
the left & 2 on the right
2 Al + 3 O2
2Al2O3
• Now that we have the O balanced we find that Al is
not, we must add 2 more Al to make it 4
4Al + 3O2
2Al2O3
• Now if you count you will find that there are 4 Al atoms
on each side and 6 O atoms. Balanced!
Example
C2 H6 + O2
C2 H6 + O2
C2 H6 + O2
C2H6 + 3.5O2
2C2H6 + 7O2
CO2 + H2O
CO2 + 3H2O
2CO2 + 3H2O
2CO2 + 3H2O
4CO2 + 6H2O
Balanced!
Tips
• When balancing equations, there are several things you can do:
• You may never put numbers that alter the formula itself.
H2O
H4O2
• Don't worry if the numbers turn out to be fractions - you can always
double or triple all the numbers at a later stage.
• If you recognize the atoms that make up a standard group such as
sulphate, nitrate, phosphate, etc. that go unmarked throughout the
chemical reaction, treat them as an indivisible item to be balanced
as a whole.
• Leave molecules representing elements until last. This means that
any numbers you put in front of those molecules won't unbalance
any other molecule.
States of Matter
• To make a chemical equation complete, the state of matter
of each substance should also be included.
• (s) solid
• (l) liquid
• (g) gas
• (aq) aqueous (dissolved in water)
• Example: solid magnesium ribbon burns in oxygen gas to
form solid magnesium oxide:
Mg (s) + O2 (g)
MgO (s)
2 Mg (s) + O2 (g)
2 MgO (s)
Description
• This activity is based on the game “Battle Ship,” where
each player attempts to find where the other player’s
ships are located on a grid. The objective of the game is
to find where the opponent’s battleship is and sink it.
• Mimicking this idea, the board would be set up with
mini-test tubes filled with water and a clear, odorless
solution that will react and change colors when a
specific solution is added to it. The tubes with the
clear, odorless solutions will act as each player’s battle
ships.
Procedure
• Start by creating a 4 by 3 grid of well plates that are filled with water. Then
make three test tubes that are filled with a clear, odorless solution. The
test tubes with the clear, odorless solution will act as the battleships and
can be placed anywhere on the grid as long as they are next to each other.
• The game will be like regular battle ship. Each player will take turns
“attacking” the opponent’s grid by dropping a solution into the beakers. If
it is a “miss,” then the solution in the test tube will either change a specific
color or not change at all. When there is a hit, the solution will change to a
specific color. The first person to sink all of the battle ships wins.
• The students will learn then about what solutions were being used during
the game and they will balance the equation between the two solutions
that caused the chemical reaction. This is so students can see what is
happening in the test tube when the two solutions are mixed.
This is what you guys are going to be doing
• Pb(NO3)2 + KI
PbI2 + K(NO3)
• Pb(NO3)2 + 2KI
PbI2 + 2K(NO3)