Transcript Stoichiometry

Stoichiometry
Mathematics & Science Center
Brainstorm
What do you already know
about chemical
reactions?
Mole
A Counting Number Equal To
6.02 X 1023 individual units.
A mass in grams equal to the
atomic mass or the formula mass
of a substance.
Set
Solve
the
for
‘x’ofrow
and
the
express
last
two
Add
Write
Add
Create
another
an
aratio
Balanced
a
additional
basic
equation
of
Equation.
row
cells.
of
the
final
in
the
answer
given
with
column
the
State cells
the
cells.
Restate
table
Problem
State
from
the
the
moles
Above
balanced
given
of
the
the
and
Reactants
equal
tocorrect
the
ratio
label.
of the
last
andunknown
given
Products
equation.
and
quantities.
unknown
in
the
Equation
two cellsininthe
theappropriate
column
quantities
5
1All
50 moles units.
? mLquantities
containing
‘x’.3
C3H8except
+ 5O2‘x’→
4 H2have
O +a 3 CO2
should
2
label.
WRITE A BALANCED EQUATION.
STATE THE PROBLEM ABOVE THE REACTANTS AND
PRODUCTS IN THE EQUATION.
Create a basic equation table
from a balanced equation.
1
Enclose the given substance
and the substance whose
amount is to be determined
in separate cells.
1.1
Add another row of cells. Restate
the moles of the given and
unknown quantities in the
appropriate units.
2
Express the moles of the given
substance with the same label as
the given quantity in the word
problem.
2.1
Express the moles of the
substance whose amount is
to be determined with the
label required for the final
answer.
2.2
Write the amount
of the given
substance in the
cell beneath this
substance in the
table.
3.1
Do you need to
convert moles
to grams?
Add another row of
cells beneath these
substances.
1.2
Yes
Write the coefficient for
each of these substances
in this second row of cells
expressed as moles.
1.3
Add an additional row of
cells. State the given and
unknown quantities.
3
Multiply the atomic
or formula mass of
the substance by
the number
of moles.
4
No
Do you need to
convert moles to
molecules?
Yes
Multiply the
number of moles
by 6.02 x 1023
No
Leave your
answer
expressed as
moles.
Set the ratio of the last
two cells in the 'given'
column equal to the ratio
of the last two cells in the
column containing "x".
All quantities except "x"
should have a label.
4
Write an "x" in the
cell beneath the
substance whose
amount is to be
determined.
3.2
Solve for 'x' and express
the final answer with the
correct label.
5
Use cross
multiplication to
solve for "x".
5.1
Cancel the unit
labels using the
one that is left for
your final answer.
Did you end up
with the right label
on your answer?
5.2
Exercise 1: Spacecraft Air
2LiOH + CO2
Li2CO3 + H2O
? grams
1400. g
2LiOH
+ CO2
2 moles
1 mole
47.8 g
44.0 g
X
Li2CO3 + H2O
1400. g
44.0 g CO2
1400. g CO2
= 47.8 g LiOH
X
44.0 g CO2
=
1400. g CO2
47.8 g LiOH
X
LiOH) (1400. g CO2)
X = (47.8g
_______________________________________________
44.0 g CO2
X = 1520g LiOH
Exercise 2: Combination Reaction
2 H2 +
O2
2H2O
? molecules
2 H2
+
O2
2H2O
1 mole
2 moles
6.02 x 1023
molecules
x
36.0 g H2O
550. g H2O
X=
550. g
36.0 g
550. g
=
6.02 x 1023 molecules O2
x
9.20 x 1024 molecules O2
Exercise 3: Flamethrower
12.9 g
?g
C3H8 + 5O2
46.9 g O2
? molecules
? mL
3CO2 + 4H2O
5.29 x 1023 molecules
21.1 mL H2O
Limiting Reactant?
Exercise 4: Combustion Reaction
C + O2
-----> CO2
A charcoal briquette weighing 45 g is placed in a jar
containing 115. g of oxygen. The briquette is lit and
a lid is placed on the jar. How many grams of CO2
can be produced by this combustion reaction?
45g
C
1mole
12.0 g
45.0 g
115 g
+ O2
1mole
32.0 g
?g
----> CO2
1mole
44.0 g
115 g
X
X = 165 g CO2
X = 158 g CO2
Oxygen is the limiting reagent!
Online Practice
Electronic Flashcard
http://garnet.acns.fsu.edu/~rlight/stoich/
What is stoichiometry?