Bell Ringer

1
Bell Ringer
Cu
AgNO3

Ag

Cu(NO3)2
?
432 g Ag
1 mol Ag
1 mol Cu
63.55 g Cu
x
x
x
107.87 g Ag
2 mol Ag
1 mol Cu
127.25 g Cu
2002 VA Chemistry SOL
2
Mass-Mass Quiz
Good job on - Calculating molar mass -
Balancing reactions with coefficients
We need to fix - remembering decomposition
reactions - making units cancel in stoichiometry
work - using the mole ratio
3
Decomposition of Carbonates
Common mistake BaCO3 ? BaO C How to balance?
What are we missing?
CO2
To remember think of a soda why do we call
them carbonated ?
H2CO3
CO2

H2O
4
Homework Answers

1. 150 L O2
2. 0.73 g Zn
3. 8.36 g NaClO3
4. 16.70 g KCl

• 93 L H2
• 14.2 L CO2
• 30.0 L CO2
• 45.0 L H2O

5
The Wisdom of Gallagher
Why are there Interstate Highways in Hawaii?
Why are there floatation devices under plane
seats instead of parachutes?
Why do we drive on parkways and park on
driveways?
Why do hot dogs come ten to a package and hot dog
buns only eight?
6
Limiting Factors and Percent Yield

• Ms. Besal
• 3/1/06

7
Hot Dogs in the News
Takeru Kobayashi of Japan downed 44½ hot dogs
in 12 minutes.
One hot dog one hot dog one bun.
WHAT IF
Mr. Kobayashi didnt do his math correctly. He
bought 5 packs of hot dogs (10 per package) and 5
packs of hot dog buns (8 per package). How many
hot dogs (according to the official formula)
could he have eaten?
Source CNN.com
8
Hot Dogs in the News
One hot dog one hot dog one bun.
WHAT IF
Mr. Kobayashi didnt do his math correctly. He
bought 5 packs of hot dogs (10 per package) and 5
packs of hot dog buns (8 per package). How many
hot dogs (according to the official formula)
could he have eaten?
Excess
5 hot dog packs
10 hot dogs
50 hot dogs
x

1 hot dog pack
Limiting Factor
40 possible hot dogs
5 bun packs
8 buns
40 buns
x

1 bun pack
Source CNN.com
9
Lets Revisit the Cookies (again)
For 1 batch

• In my pantry, I have
• 5 cups of flour
• 16 Tbsp of butter
• lots of everything else

• 2.25 cups flour
• 8 Tbsp butter
• 0.5 cups shortening
• 0.75 cups sugar
• 0.75 cups brown sugar
• 1 tsp salt
• 1 tsp baking soda
• 1 tsp vanilla
• 0.5 cups Egg Beaters
• 12 oz. Chocolate chips

How many batches of cookies can I make?
10
Lets Revisit the Cookies (again)
For 1 batch
How many batches of cookies can I make?
5.5 cups

• 2.25 cups flour
• 8 Tbsp butter
• 0.5 cups shortening
• 0.75 cups sugar
• 0.75 cups brown sugar
• 1 tsp salt
• 1 tsp baking soda
• 1 tsp vanilla
• 0.5 cups Egg Beaters
• 12 oz. Chocolate chips

16 Tbsp
EXCESS
1 batch cookies
5.5 c flour
x

2.25 c flour
2.4 batches
1 batch cookies
16 Tbsp butter
x

8 Tbsp butter
2.0 batches
11
Now I Want to Bake a Cake!
But do I have all the ingredients I need?
How much flour do I have left after baking all
those cookies?
SOME FLOUR LEFT OVER
GONE!
2.25 cups flour
4.5 cups flour used
2.0 batches
x

1 batch cookies
5.5 cups 4.5 cups 1.0 cups left
12
Limiting Reactants in Chemistry
5.0 moles of chlorine gas react with 5.0 moles of
sodium to produce sodium chloride. Which reagent
is the limiting factor? How much of the excess
reactant is left over?
Cl2 (g)

Na
NaCl
EXCESS
2 givens 2 equations!
2 mol NaCl
5.0 mol Cl2
x

10. mol NaCl
1 mol Cl2
2 mol NaCl
5.0 mol Na
x

5.0 mol NaCl
5.0 mol Cl2 given
2 mol Na
2.5 mol Cl2 used
1 mol Cl2
2.5 mol Cl2
5.0 mol Na
x

2.5 mol Cl2 left
2 mol Na
13
Practice Problems
1.
3 CuSO4

2 Al
Al2(SO4)3
3 Cu

1 mol CuSO4
3 mol Cu
20.0 g CuSO4
x

0125 mol Cu
x
159.61 g CuSO4
3 mol CuSO4
20.0 g Al
1 mol Al
3 mol Cu
1.11 mol Cu
x
x

26.98 g Al
2 mol Al
1 mol CuSO4
26.98 g Al
2 mol Al
20.0 g CuSO4
x

x
x
159.61 g CuSO4
1 mol Al
3 mol CuSO4
2.25 g Al
20.0 g Al 2.25 g Al
17.8 g Al
EXCESS
USED
14
Practice Problems
2.
2 H2 (g)

O2 (g)
2 H2O
USED
5.0 g H2 0.63 g H2
4.37 g H2
EXCESS
15
On Perfection

• Perfection never exists in reality, but only in
  our dreams.
• - Dr. Rudolf Dreikurs
• Perfection is our goal, excellence will be
  tolerated.
• - J. Yahl

16
Get Real!
Johnny took a quiz yesterday. He missed 4
questions and earned 63 points out of 70.

• Was he perfect?
• What was his possible score?
• What was his actual percent score?

70 points 100
90
17
Get Real!
Ms. Besal ran a reaction in her lab yesterday.
She predicted that 183 grams of product would be
formed. The reaction only yielded 162 grams of
product. But she looked really cool in her lab
coat.

• Was her reaction perfect?
• What was the percent yield?

162 grams
100
88.5
x

183 grams
18
Practice 20 on Homework
What volume of ammonia can be obtained by
reacting 100 L of nitrogen gas with an excess of
hydrogen, if the yield is 90?
H2
NH3
N2

100 L N2
1 mol N2
2 mol NH3
22.4 L NH3
x
x
x

22.4 L N2
1 mol N2
1 mol NH3
200 L NH3
THEORETICAL YIELD
200 L NH3 x 90 180 L NH3
ACTUAL YIELD
19
Next Class

• Quiz on Volume Conversions
• Mass-Volume
• Volume-Mass
• Volume-Volume
• 2 questions, 10 points each
• Watch significant figures labels!