Transcript Unit 5 - Counting Particles

Unit 5 - Counting Particles
Chem Catalyst – 3/24
• Up front is a garbage bag full of
Styrofoam peanuts. We want to count
how many peanuts are in the bag.
Describe a few ways you could
determine how many peanuts were in
the bag.
Chem Catalyst
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If you have the following relationships:
1 box of nails = 100 pieces of nails
25 pieces of nails = 15.0 g of nails
1000 g = 1 kg, 1 kg = 2.20 lbs
How many pounds of nails are there in
14,000 pieces of nails?
What do these pictures have
in common?
Think back to yesterday’s class
• What counting units did we use in the lab
yesterday?
• What are some other common counting
units?
• Dozen, gross, score
• In chemistry, the “mole” is a counting unit.
Counting units
• 1 dozen = 12 particles of something
• 1 gross = 144 particles of something
• 1 score = 20 particles of something
• 1 mole = 6.02 x 1023 particles of something
• “Avagadro’s number”, NA
The Mole – Avogadro’s Number
6.02 x 1023
• Amedeo Avogadro came up with
“the mole” as a counting unit in
chemistry.
• The mole is very useful for
determining the number of particles
in a sample of a certain substance,
like titanium, gold, table salt, etc.
• Doing experiments, Avogadro
found that 12 grams of carbon =
6.02 x 1023 atoms of carbon.
How big is the number 6.02 x
23?
10
602,000,000,000,000,000,000,000 written in
standard format
• 1 mole of rice = cover all land 75 ft. thick!
• 1 mole marshmallows = cover U.S. in 650
miles of marshmallows!
• 1 mole of basketballs = fill a ball bag the size
of earth
• If every living person on earth started counting
one paperclip each second, it would take 4
million years to reach 6.02 x 1023 paperclips!
Count how many dozen
paperclips are on the next slide
How many paperclips would
be in 2 moles of paperclips?
Just like we can have 1/2 of a dozen:
How many particles would be
in 0.5 moles?
Substance
# of moles
# of particles
Total # of atoms
He (g)
1
6.02 x 1023
6.02 x 1023
He (g)
0.5
3.01 x 1023
3.01 x 1023
He (g)
2.0
12.04 x 1023
H2 (g)
1
6.02 x 1023
H2 (g)
0.5
3.01 x 1023
H2 (g)
2
Cu (s)
1
Cu (s)
0.1
H2O(l)
1
H2O(l)
0.5
12.04 x 1023
24.08 x 1023
0.602 x 1023
18.06 x 1023
3.01 x 1023
Chem Catalyst
All problems below are about methane,CH4.
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How many molecules (particles) of methane are
in 1 mole?
– In one molecule of methane, how many atoms of
hydrogen do you have?
– In 2.0 moles of methane, how many molecules
(particles) of methane do you have?
– In 2.0 moles of methane, how many total atoms
of H and C do you have?
The car as a molecular formula
• 1 car = __ Tires, __Windshield Wipers
and __Steering Wheel
• As a formula,1 car = T W S
If I had 3 cars…….
How many tires would I have?
How many wipers?
How many steering wheels?
Recall our car example
• 1 car = T4W2S
If I had 1 dozen cars, how many tires would I
have? Wipers? Steering wheels?
How many dozen tires would I have?
How many dozen wipers?
How many dozen steering wheels?
Recall our car example
• 1 car = T4W2S
If I had 1 gross of cars, how many tires would
I have? Wipers? Steering wheels?
How many gross of tires would I have?
How many gross of wipers?
How many gross of steering wheels?
Chem Catalyst
• How many moles of hydrogen are there
in one mole of water?
• How many moles of oxygen are there in
one mole of water?
• How much do you think one mole of
water molecules is? 1 liter? 1 mL?
1000 L?
Paperclip counting challenge
Chem Catalyst
Imagine you have 4 moles of hydrogen (H2) gas
and 3 moles of H2O.
• How many grams of hydrogen gas would you
have? How many molecules of hydrogen gas
would you have? How many atoms of
hydrogen would you have?
• How many grams of water would you have?
How many molecules of water would you
have? How many H and O atoms would you
have?
Molar Mass Worksheet
Chem Catalyst
• What is the molar mass of ammonia,
NH3? Write the molar mass as an
equality.
1 mole of NH3 = ___ grams of NH3
• ESTIMATE – How many moles of NH3
do you think you would have if you had
50 grams of NH3?
• GET A PERIODIC TABLE AND CALCULATOR!
Gram-Mole and Mole Gram
Conversion Worksheet
Re-work problem assignment
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Test Wednesday
More than a trillion: 2, 3, 4
Moles within moles: 9a-c, 11
Molar mass: 5a-c
Gram-Mole conversions: 1, 2, 8, 9, 10
ChemCatalyst
1.) Find the molar mass
of aspartame and write
it as an equality.
1 mole of aspartame =
____g of aspartame
2.) If you have 256
grams of aspartame,
how many moles would
that be?
Which can has more
molecules?
• Regular soda: 40 g of fructose.
• Diet soda: 0.225 g of aspartame
• Use the factor label method to calculate
the number of moles of each molecule
in the two cans.
Chem Catalyst
• What is the molar mass of copper (II)
chloride, CuCl2? Write your answer as
an equality.
• How many grams are in 3.5 moles of
copper (II) chloride?
• How many moles are in 40 grams of
copper (II) chloride?
• If you have 0.81 moles of CuCl2, how
many molecules (particles) of CuCl2
would you have?
Nail Lab – Day 1
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1.) Wear goggles!
2.) Label beaker with group names using
marker provided.
3.) Weigh empty beaker to nearest 0.01g
4.) Mr. Fritz will pour 50mL of CuCl2
solution into your beaker.
5.) Weigh 2 nails to nearest 0.01g
6.) Make observations about nails and
CuCl2 solution BEFORE putting nails in.
7.) Put nails in copper chloride. Make
observations after putting nails in.
Chem Catalyst
• What is the molar mass of calcium
bromide, CaBr2? Write your answer as
an equality.
1 mole of CaBr2 = ___ grams of CaBr2
• How many moles are in 30 grams of
calcium bromide?
• How many molecules (particles) are in
that many moles of CaBr2?
*Hint = use Avagadro’s Number!
Nail Lab – Day 2
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=?
1.) Wear goggles!
2.) Remove nails with tweezers
3.) Scrape precipitate from the nail into your
beaker with a plastic spoon.
4.) Dry nails with paper towel.
5.) Pour (decant) the solution in the waste
beaker at your lab table. DON’T POUR OUT
COPPER PRECIPITATE!
6.) Rinse copper twice with water, once with 1M
HCl, once again with water.
7.) Weigh dry nails, record data, throw nails
away.
Chem Catalyst
• Lead (II) sulfate, PbSO4, was used as a
pigment in paints. How many moles of
lead sulfate are in 50.0 g of lead(II)
sulfate? How many atoms of oxygen
are present?
Chem Catalyst
• What do you think is happening to the
copper and the iron in the nail lab?
Calculations
• Do the calculations. Then compare to
Dr. Chen’s numbers.
• Mass of iron nails before = 5.12 g
• Mass of iron nails after = 2.23 g
• Mass of copper powder = 2.55 g
Chem Catalyst – 3/16/09
Below is a chemical “sentence” describing the
formation of a very toxic substance, hydrogen
cyanide.
NaCN (s) + HCl (aq) → NaCl (aq) + HCN (g)
What kinds of information does this chemical
notation contain? List at least four pieces of
information contained in this chemical notation.
Announcements
• MOLE TEST – If you have not taken it yet, you MUST
come to my flex tomorrow to complete it – or come
before/after school.
• RETAKES – You may retake the back portion of the
exam for up to 80% credit by the end of this week.
Flex, before school, or after.
LOOKING AHEAD……..
• NO SCHOOL – NEXT Monday, 3/23 – PD Teachers
• PT Conferences – NEXT Thursday, 3/26
• End of Marking Period – 4/3 – only 3 weeks away!
• SPRING BREAK – 4/10-20 
Making Sense
CuCl2(aq) + Fe(s) ----> FeCl2(aq) + Cu(s)
Brownishliquid
Reactants:
Products:
CuCl2(aq) + Fe(s) ----> FeCl2(aq) + Cu(s)
Symbol
What it
Represents
Symbol
CuCl2

(aq)
FeCl2
+
(aq)
Fe
Cu
(s)
(s)
What it
Represents
Chem Catalyst – 3/17/09
Consider the following reaction:
AgNO3 (aq) + KCl (aq) → KNO3 (aq) + AgCl (s)
• What do you expect to observe if you
carried out the reaction?
• Translate the above chemical equation into
writing, describing what is taking place.
Making Sense
• What are some observations you
made?
• What types of observations are
asociated with the changes that took
place? (aq, s, g)
• Why do you think there are two
equations for some of the procedures?
Chem Catalyst – 3/18/09
• The following two equations both describe
what happens when dry ice is placed in
water:
CO2 (s) → CO2 (g)
CO2 (s) + H2O (l) → H2CO3 (aq)
• What differences do you see in these two
equations?
• Why do you think two equations are needed
to describe what happens?
Making Sense
• Physical Changes: Changes in the
appearance or form of a substance.
Ex:
CO2 (s) → CO2 (g)
H2O (l) → H2O (g)
H2O (s) → H2O (l)
• Chemical changes: New substances with
new properties are produced.
Ex:
CO2 (s) + H2O (l) → H2CO3 (aq)
AgNO3(aq) + KCl(aq) → KNO3(aq) + AgCl (s)
Is dissolving a chemical
change or a physical change?
Demonstration:
CoCl2(s) --> CoCl2(aq)
Often written as: CoCl2(s) -->
Check-In
• Does the following chemical equation
describe a physical change or a chemical
change? Explain how you can tell.
C17H17O3N(s) + 2C4H6O3(l) → C21H21O5N(s) + 2 C2H4O2(l)
Chem Catalyst – 3/19/09
• Consider the following reactions:
1.) CaCO3 (aq) --> CaO (aq) + CO2 (g)
2.) CO2 (g) + NaOH (aq) --> NaHCO3 (aq)
• How are these two reactions different?
(Look at the whole reaction)
• How would you describe, in words, what
happens to the reactant molecules in each
case?
TOXINS – What’s your reaction?
• We can study chemical reactions by learning
about how toxic substances react with your body.
• Ex: Phosgene, COCl2 (g) – Damages eyes, nose,
throat, lungs
Verbal description: Phosgene gas reacts with water
(tears, saliva, mucuous) to produce aqueous
hydrochloric acid and carbon dioxide gas.
COCl2 (g) + H2O (l) --> 2 HCl (aq) + CO2 (g)
• Used as a biological weapon in World War I
Chem Catalyst – 3/24/09
• Consider the following reaction.
Na2CO3 (aq) + CaCl2 (aq) --> NaCl (aq) + CaCO3 (s)
• Describe what you will observe when
Na2CO3 (aq) and CaCl2 (aq) are mixed.
• Will the mass increase, decrease, or stay
the same after mixing? Explain.
Results from Lab
1.)
NaCl (s) --> NaCl (aq)
– Did the mass change for this reaction?
– Why or why not?
Results From Lab
Na2CO3 (aq) + CaCl2 (aq) --> NaCl (aq) + CaCO3 (s)
– Did the mass change for this reaction?
– Why or why not?
Results From Lab
Na2CO3 (aq) + C2H4O2 (aq) -->
NaC2H3O2 (aq) + H2O (l) + CO2 (g)
– Did the mass change for this reaction?
Why or why not?
– Do gases have mass?
Balancing Reaction Notes
• Law of conservation of mass: Matter
can be neither created nor destroyed.
• Atoms do not come in and out of
existence. They are simply rearranged.
• Since atoms have mass, the mass of
reactants and products does not
change.
Check-In
• Consider the following reaction:
CuCO3 (s) + H2SO4 (aq) --> CO2 (g) + CuSO4 (aq) + H2O (l)
• Describe what you will observe when CuCO3 (s)
and H2SO4 (aq) are mixed.
• Will the mass increase, decrease, or stay the same
after mixing? Explain.
Chem Catalyst
• Consider the following reaction:
Fe (s) + CuCl2 (aq) --> FeCl2 (aq) + Cu (s)
• Describe what you will observe when Fe (s) and
CuCl2 (aq) are mixed.
• Will the mass increase, decrease, or stay the same
after mixing? Explain.
Questions
• How did we know that iron was being
used up in the reaction?
• What caused the reaction to stop?
Which reactant was used up? How do
you know?
What do you think is happening to
the atoms in the reaction?
Particle representation
Aqueous copper (II) chloride is reacting with solid iron to
form solid copper and aqueous iron(II) chloride.
Chemical formula representation:
Particle representation:
What is a “coefficient” and
what does it mean?
__Fe(s) + __CuCl2(aq) ---> __Cu(s) + __FeCl2(aq)
Our data:
Iron used up = 5.12g - 2.23 g = 2.89 g Fe
Copper formed on nail = 2.55 g Cu
ChemCatalyst
Iron (Fe) is the main component in nails used for
building things. Below is the reaction of iron nails
with copper chloride:
__Fe(s) + __CuCl2(aq) ---> __Cu(s) + __FeCl2(aq)
1.) Balance the equation
2.) In what ratio should you mix iron and
copper chloride to produce the maximum
amount of solid copper?
Balancing Equations
___C + ___H2O --> ___CO + ___H2
Particle Representation:
ChemCatalyst Review
Balance the equation below:
__ C2H6O + __ O2 __ CO2 + __ H2O
What type of reaction is below?
(single exchange, double exchange,
combination or decomposition?)
1.) Cl2(g) + 2NaBr(s) → 2NaCl(s) + Br2(s)
2.) CO2 (g) + NaOH (aq) → NaHCO3 (aq)
3.) 2AgCl(s) + BaBr2(aq) → 2AgBr(s) + BaCl2 (aq)