In this unit we move up from writing words (chemical formulas) to
sentences and maybe even paragraphs (chemical reactions). Of
writing sentences means that one must be able to write words so in the
of chemistry one must be able to write formulas before attempting to
equations for chemical reactions.
Stoichiometry is simply a fancy word for calculating amounts (grams,
liters) in chemical reactions. The key part of this process is
the the mole relationships in the chemical equation. This
balancing a chemical equation as the first step.
The process of balancing a chemical equation is a
of a basic scientific principal of the Law of Conservation of Matter.
law states that matter is neither created or destroyed (or matter is
in all non nuclear reactions). In chemistry we demonstrate this
writing balanced equations. A balanced equation is simply one
the number of each kind particle on each side of the equation is the
The first step in writing a balanced equation is to write a
equation, one with correct formulas for reactants
(on the left side of the arrow) and products
(on the right side of the arrow). Then one needs to change the
of particles on each side until they are all equal. We do this by
coefficients in front of the correct
(we do NOT change the formulas).
Once the equation is balanced, the stoichiometry part is possible.
is because the coefficients of the
equation give the mole ratios of the compounds.
is why we spent so much time in the last unit on moles. The mole is the "super secret unit" of chemistry
because almost all of the calculations that are done in chemistry
moles. If one can find the number of moles of a reactant or
then it is only one simple additional step of using the coefficients of
balanced equation to calculate the moles of anything else in the
Using this process one can for example, calculate the volume of
necessary to "burn" 120 grams of sugar when it is eaten.
Unit VII Chemical Reactions
Be able to predict synthesis, single replacement, double replacement,
and combustion reactions.
Be able to balance chemical reactions, including redox reactions
Be able to calculate mass, mole, and volume relationships in chemical
Terms: chemical reaction, reactant, product, single
double displacement, decomposition, synthesis, combustion,
mass-mass problem, mass-mole problem, mass-volume problem,
reduction, oxidizing agent, reducing agent.
Suggested Problems: Read Chapter 9 and Chapter 25
pgs 243-247 (43-46, 48-55, 58-61) Review (1-12)
pgs 646-647 (39, 43, 45-47, 49, 50)
Return to the HHS Science Home Page
from UNC, Chapel Hill
On the ChemTeam site there is a Stoichiometry Worksheet (#3 under Lab Experiments
& Worksheets). There are 10 Stoichiometry problems here. I
will give you 1 extra credit point for each correctly worked problem.