Ch. 11 Blue Book:
Ch. 11 HW #1-11 & 15
Yes, more math!!
Balancing Equations
What do you remember? (lets just brainstorm!)
What do the balanced equations tell you?
Why? Law of Conservation—who can explain?
How do Chemists use this relationship?
Like a recipe!
Let’s try one: Ca + H2O
Ca(OH)2 + H2
Ca + 2 H2O
Ca(OH)2 + H2
And another : C2H6 + O2
CO2 + H2O
2C2H6 + 7O2 4 CO2 + 6 H2O
Balancing Equations
Video’s?
http://www.youtube.com/watch?v=RnGu3xO2h74&play
next_from=TL&videos=h7PQ10ClYzI
Review: Mass to Mass Example 1
Given a certain amount of a reactant how do we find
the mass of a certain product?
How much ethane would it take to get 20 grams of
carbon dioxide?
1.
2.
3.
Balance Equation
Identify known & unknown
Equation to solve
a. Mass of known to moles of known
b. Moles known to moles unknown
c. Moles unknown to mass unknown Balance Equation
2C2H6 + 7O2
4CO2 + 6 H2O
• Using
molecular
mass g/mol
Mass
Moles
• Using the ratio in a
balanced equation
allows us to convert
from one substance
to another.
• Using
molecular
mass g/mol
Mass
Review: Mass to Mass Example 2
How many grams of glucose form when 88.0 g of
CO2 reacts?
CO2 + H2O
C6H12O6 + 6 O2
First what are the steps? Using words write them
down.
Now what purpose does each step serve? Using
words!
Share with the class!
Calculate
Answer is 60.0g C6 H12O6
Now Mass to Volume…
finally Ch. 11 Stuff!
What are the steps?
Any relationship between moles and
volume with gases?
In groups, diagram the steps you
think needed to go from mass to
volume, refer to my diagram that goes
from mass to mass!
Mass to Volume cont..
Moles
Mass
Moles
Balance Equation
2. Identify known & unknown
3. Mass to Moles (known)
Volume 4. Moles (known) to Moles
(unknown)
5. Moles (unknown) to
Volume of unknown (22.4
dm3 = 1 mole)
1.
Ch 11 Mass to Volume Example 1
Calculate the volume of oxygen produced at STP by the
decomposition of 10.0 g of potassium chlorate, KClO3.
KClO3
KCl + O2
Hint
Balance the equation
I.D. known & unknown
Convert the grams to moles
Convert moles of KClO3 to moles of O2
Convert moles of oxygen to volume using our handy 22.4
dm3 = 1 mol of any gas @STP!
Answer: 2.74 dm3 O2
Ch 11 Mass to Volume Example 2
How many cubic centimeters of hydrogen are
produced by the reaction of .750 grams of sodium
metal with excess water?
Na + H2O
NaOH + H2
Hint
Balance the equation
Convert the sodium to moles
Convert moles of sodium to moles of hydrogen
Convert moles of hydrogen to volume using our handy
22.4 L = 1 mol of any gas!
Throw in a cm to dm conversion
Answer: 365 cm3
Ch 11 Mass to Volume Example 3
Al reacts with HCl to produce aluminum chloride and
hydrogen gas. How many dm3 of hydrogen at STP are
produced if Al reacts with an HCl solution which has a
mass of 80.0g and contains 70.0% water?
Al + HCl
AlCl3 + H2
If 80.0 g of a solution of HCl is 70% water then it is
30% pure HCl, use part to whole:
30g pure HCl/100 g solution of HCL
ANSWER: 7.36dm3 H2
Example 4
How many grams of ammonium sulfate must react with
excess sodium hydroxide to produce 400 cm3 of
ammonia measured at 27oC and 98.0 kPa?
(NH4)2SO4 + NaOH
Na2SO4 + NH3 + H2O
Answer: 1.04 g (NH4)2SO4
Ch 11 Mass to Volume HW
#1-11 & 15
Blue Book
Ch. 12 Volume to Volume: How do
chemists convert volume to volume???
First Step?
Balance the Equation
Balance
the Eqn
Second Step?
ID known & unknown
Third Step
Volume
Volume of known to Moles
of known
Fourth Step?
Moles of known to moles
of unknown
Moles
(Ratio)
Next?
Moles of unknown to
volume of unknown.
Volume
Volume to Volume Example 1
If 6.00 dm3 of oxygen are available to burn
carbon disulfide, how many dm3 (liters) of
carbon dioxide are produced? The products of
the combustion of carbon disulfide are carbon
dioxide and sulfur dioxide.
CS2 + O2
CO2 + SO2
1.
2.
3.
Volume to Mole (known)
Mole (known) to Mole (unknown)
Mole (unknown) to Volume (unknown)
2.0 dm3 CO2
Anybody see a shortcut??
All gases
So…
6.00dm3
1 dm3 CO2
3dm3 O2
= 2.oo dm3 CO2
Careful… only if the gases are measured under the same
conditions of temperature & pressure then 3 volumes O2 = 1
volume CO2 or 3 dm3 O2 = 1 dm3 CO2 (see p. 120 in Blue Book)
Volume to Volume Example #2
When a hydrocarbon such as ethylene burns
completely in oxygen, the products are carbon dioxide
and water. Calculate the dm3 of air required to burn
completely 15.0 dm3 of ethylene gas, C2H4, measured at
STP. Assume air contains 21.0% oxygen by volume.
CO2 + H2O
C2H4 + O2
1.
2.
3.
Volume to Mole (known)
Mole (known) to Mole (unknown)
Mole (unknown) to Volume (unknown)
Answer: 214 dm3 air
Volume to Volume Example #3
How many liters (dm3) of air measured at 98.5
kPa and 100o C are required to produce 200dm 3
of CO2 measured at the same pressure and 20o
C? Assume that air contains 21% oxygen by
volume and that the CO2 is being produced from
CO.
CO + O2
CO2
Balance Equation
2. Old/New Chart to find missing volume
3. Conversions?
1.
1 dm3 O2 = 2 dm3 CO2
21 dm3 O2 = 100 dm3 air
4. Put it all together
ANSWER: 606 dm3 air
Chapter 11 Mass-Volume HW
#1-11 & 15
Chapter 12 Volume-Volume HW
#1-10
*Chapter 11 & 12 Test: 5/3 & 5/6*
(B-day)
(A-day)