Download - STOICHIOMETRY_1
-
7/27/2019 STOICHIOMETRY_1
1/23
Stoichiometry
-
7/27/2019 STOICHIOMETRY_1
2/23
Just what is stoichiometry?
The word stoichiometry is derived
from two Greek words: stoicheion(meaning element) and metron
(meaning measure).
-
7/27/2019 STOICHIOMETRY_1
3/23
-
7/27/2019 STOICHIOMETRY_1
4/23
How does it work?
Then the chemist uses the equation to
guide them in calculating theproducts. Since stoichiometry is used
to predict things in the perfect
world, we can expect that thereaction in real life wont create the
maximum amount of product.
-
7/27/2019 STOICHIOMETRY_1
5/23
The chemical equation is the
chemists recipe!
By using the chemical equation, chemists can
calculate the amount of materials needed orthe approximate amount of materials produced
(the amount of materials actually produced in
the lab is approximate since we do not live in a
perfect world).
-
7/27/2019 STOICHIOMETRY_1
6/23
How do I use the chemical
equation?
The chemical equation is written like a
mathematical expression. When balanced, thecoefficients tell how many moles of each
reactant or product is needed or expected.
-
7/27/2019 STOICHIOMETRY_1
7/23
Example:
2H2 + O2 2H2O
One way to understand the information conveyed by
a chemical equation is to convert the equation into
an English sentence.
-
7/27/2019 STOICHIOMETRY_1
8/23
So: 2H2 + O2 2H2O
This equation really says: two moles of H2
added to one mole O2 yields two moles ofwater.
(the coefficients tell how many moles, atoms or
molecules of each chemical are needed in therecipe)
-
7/27/2019 STOICHIOMETRY_1
9/23
Quantitative Information from
Balanced Equations
In addition to being both a qualitative and
quantitative statement of fact, a balancedchemical equation is an algebraic equality in
which the arrow is the equal sign. This means
that we can manipulate a balanced chemicalequation in much the same way as we can
manipulate any other algebraic equality.
-
7/27/2019 STOICHIOMETRY_1
10/23
Consider the combustion of propane.
C3H8 + 5 O2 3CO2 + 4H2O
-
7/27/2019 STOICHIOMETRY_1
11/23
Stoichiometry has 5 basic steps:
Step 1: Write and balance the equation
-
7/27/2019 STOICHIOMETRY_1
12/23
Step 2: Write in all information given
(make sure to identify what you aretrying to find!)
-
7/27/2019 STOICHIOMETRY_1
13/23
Step 3: Convert everything to moles
-
7/27/2019 STOICHIOMETRY_1
14/23
Step 4: Use mole ratio to solve for what
you are trying to find (you may alsouse a proportion to solve the
problem.)
-
7/27/2019 STOICHIOMETRY_1
15/23
Step 5: Convert everything into the
required unit if needed.
-
7/27/2019 STOICHIOMETRY_1
16/23
What is a mole ratio?
Mole Ratios: The mole ratio is based on
the balanced chemical equation.
-
7/27/2019 STOICHIOMETRY_1
17/23
Example of a mole ratio:
CH4 + 2O2 CO2 + 2H2O
The mole ratio of CH4:O2 is 1:2. Another
way to write this is CH4.2O2
-
7/27/2019 STOICHIOMETRY_1
18/23
How do you use a mole ratio?
The mole ratio is an equivalent which
means that you can arrange the ratioin any way needed.
-
7/27/2019 STOICHIOMETRY_1
19/23
Example of a mole ratio problem:
N2 + 3H2
2NH3
Write the molar ratios for N2 and H2.Write the molar ratios for NH
3and H
2.
Convert the ratios above into afraction.
-
7/27/2019 STOICHIOMETRY_1
20/23
Examples of a mole-mole
stoichiometric problem:
2H2 + O2 2H2O
1. How many moles of H2O are
produced when 5 moles of oxygen are
used?
-
7/27/2019 STOICHIOMETRY_1
21/23
Examples of a mole-mole
stoichiometric problem continued:
2H2 + O2 2H2O
2. If 3.00 moles of H2O are produced,
how many moles of oxygen must beconsumed?
-
7/27/2019 STOICHIOMETRY_1
22/23
-
7/27/2019 STOICHIOMETRY_1
23/23
Example of a mole-mass
stoichiometric problem:
2H2 + O2 2H2O
If 3.00 moles of oxygen are completely
converted to water, what is the mass of
the water produced?