Transcript Chemical Quantities

Chemical Quantities
The Mole
But first…
1. CuCl2
2. Na3PO4
3. S2O5
4. PbSO4∙2H2O
5. HNO2
6. Silver acetate
7. Gold (III) iodide
8. Dinitrogen tetrabromide
9. Cuprous nitrate tetrahydrate
10. Hydrofluoric acid
Answers
Pick out the
mistake and
write it down in
1.
your notes…do
not say it out
loud, or in a
whisper, or in
4. Lead (II) sulfate dihydrate
sign language,
or in any way
that would let
someone else
know the
answer before
they could
figure it out on
their own.
Copper (II) chloride or cupric chloride
2. Sodium phosphate
3. Dinitrogen pentoxide
or
plumbous sulfate dihydrate
5. Nitrous acid
6. Ag2C2H3O2
7. AuI3
8. N2Br4
9.
Cu(NO2)2 ∙ 4H2O
10. HF
And second…
The portfolio…
Sections
Notes—date each day, chronological order and not kept in a spiral
notebook.
HW—dated and put in chronological order
Quests—see HW
Tests—see HW
General—everything that doesn’t have a home in the first set of sections
goes here.
Daily Journal…
The Daily Journal
1. A statement of what was done that day. (We took notes over moles and
Avogadro’s number).
2. ****A summary of your notes. Explain in detail in your own words what
was covered in the notes for that day. Or explain what the purpose of the
lab was, etc.****
3. A couple statements about what you do not clearly understand or what you
could not clearly describe in part #2 above.
4. What you are doing that night or what you have already done that night
concerning this class.
Ready??
Now we can begin with notes…
Goals for Learning
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To convert between moles and number of particles
To convert between mass and moles
To convert between moles and gas volume at STP
To use molarity in conversions involving solutions
To calculate the percent composition of a compound
To find an empirical formula from percent composition
To use an empirical formula to find a molecular formula
Organization of Unit
Volume of
a solution
Mass
Percent
composition,
empirical and
molecular
formulas
Number of
Number of
Moles
particles
Volume of a
gas at STP
Objectives
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•
Explain what a mole is
Convert between moles and number of particles
Define molar mass
Find the molar mass of an element using the
periodic table
• Calculate the molar mass of a compound
• Use molar mass to convert between mass and
moles
Key Terms
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•
Mole (mol)
Avogadro’s number
Atomic mass
Molar mass
Measuring Matter
• All matter is made of different kinds of particles.
• These particles can be molecules, atoms or ions.
• Elements such as helium and iron exist as single
atoms.
• Other elements, like H, O and N are diatomic
molecules.
• Molecular compounds, like CO2 and water, also
exist as molecules.
Measuring Matter
• Ionic compounds, like ammonium carbonate,
consist of cations and anions in formula units.
• Depending on the substance, different names for
the particles are used.
• In this unit, all atoms, molecules and formula
units are referred to as particles.
The Mole
• The particles in matter are very, very small—too small
to see, even with a microscope.
• Counting the number of particles in a sample is not
possible.
• Instead of counting them, chemists measure the
number of particles with a unit called the mole.
• The abbreviation for mole is mol (I suppose there is a
logical reason for this).
• The mole is a unit for measuring the amount of
substance.
The Mole
• The word mole means a number, similar to the
word dozen.
• 1 dozen eggs = 12 eggs
• 1 mole eggs = 6.022 x 1023 eggs
• One mole of any substance contains 6.022 x 1023
particles.
• These particles can be atoms, molecules or
formula units.
The Mole
• The number 6.022 x 1023 is called Avogadro’s
number.
• It is a very, very large number.
• A mole of eggs is more eggs than have ever been
eaten in the history of the world.
• If you stacked a 6.022 x 1023 sheets of paper, the pile
would reach to the sun and back more than a million
times!
• However a mole of molecules, atoms and formula
units is not very big.
Today…
• Get ready for practice…
• Notes to fill in the flow chart from Friday
• Journals—in class—5 minutes before the bell—you must write
the entire time…
Time to Practice
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
NiCl2
K3PO4
S2Cl2
H2CO3
Cu(NO3)2
Sodium hypochlorite
Silver bromide
Hydrochloric acid
Strontium permanganate
Sulfur trioxide
Time to Practice
1.
Nickel (II) chloride or nickelous chloride or #23 chloride
2. Potassium phosphate
3. Disulfur dichlorine
4. Hydrocarbonic acid
5. Copper (II) nitrate or Cupric nitrate
6. NaClO
7. AgBr
8. HCl
9. Sr(MnO4)2
10. SO3
Time to Recall
1. What is the date of Mole Day?
2. What time does it begin? End?
3. Write down the food you will be bringing in on Mole
Day.
4. If you had a mole of bananas, how many bananas
would you have?
5. What is this # called? (Name of dude?)
Mole-Particle Conversions
Volume of
a solution
Mass
Percent
composition,
empirical and
molecular
formulas
Number of
Number of
Moles
particles
Volume of a
gas at STP
Use
Avogadro’s
# of 1 mole =
6.022 X 1023
particles
Mole-Particle Conversions
• Chemists use Avogadro’s number to calculate the
number of particles in a sample of matter.
• Suppose you are told that balloon contains 2.00 mol
of the gas argon–and nothing else.
• You want to know how many particles are in the
balloon.
• You want to change the measurement units from
moles to particles.
• Moles Ar  particles Ar
Mole-Particle Conversions
• Your conversion factor is 1 mol Ar = 6.022 x 1023
particles Ar.
• Write the given number and unit. Include the
chemical symbol or formula of the substance.
• Set up a factor label grid.
• Use the conversion factor in the grid—making sure to
align units so that they will cancel.
• Give the answer with the correct unit and the correct
number of significant digits.
Mole-Particle Conversions
• You try…
• How many moles are in 4.35 x 1024 molecules of
CO2?
• How many formula units are in 3.15 mol of sodium
oxide?
Molar Mass
• We know that 1 mole of a substance is a certain
number of particles—regardless of what the particles
are.
• 1 mole of donuts is 6.022 x 1023 donuts
• 1 mole of desks is 6.022 x 1023 desks
• 1 mole of ¥ is 6.022 x 1023 ¥
Molar Mass
• 1 mole of a substance also has a certain mass—but it
is different for every substance.
• 1 mole of donuts does not have the same mass as 1
mole of desks, but they still contain the same number
of each.
Molar Mass
• It is impossible to count the particles in a sample of matter
but it is easy to find the sample’s mass.
• If you know the mass of a substance, you can determine the
number of moles in it.
• To make a mass-to-mole conversion, you need to know
about another piece of information from the periodic table.
• Atomic number—number of protons and electrons in an atom
• Atomic mass or molar mass is the mass of one atom of the
substance or the mass of one mole of the substance.
Molar Mass
• If you want to know the atomic mass (mass of one atom) the
number has units of amu (atomic mass units).
• If you want to know the molar mass (mass of one mole of
atoms) the number has units of g/mol (grams of substance
per mole of substance).
The Molar Mass of Elements
• The molar mass of carbon is 12 g/mol.
• The molar mass of oxygen is 16 g/mol.
• This means that 6.022 x 1023 atoms of carbon (1 mol) has a
mass of 12g.
• This also means that 6.022 x 1023 atoms of oxygen (1 mol)
has a mass of 16g.
Review Mini
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What is a dozen?
What is a mole?
How many atoms of H are in a dozen of H?
How many atoms of H are in a mole of H?
What is the mass of one H atom?
What is the mass of 1 mole of H atoms?
What is the mass of 1 O atom?
What is the mass of 1 mole of O atoms?
What is the mass of 1 mole of H2O?
Today…
• Short review time…
• Get boards
• Notes—molar mass, mass to mole conversions, gas volume to
mole conversions, solution volume to mole conversions, percent
composition and empirical formula concept…
• HW—review 1 and 2 due tomorrow
Review time…
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
CaI2
NaNO3
FeCl3
SO2
CoF2∙3H2O
Lithium nitride
Aluminum hydroxide
Carbon tetrabromide
Cupric nitrite
Magnesium acetate dihydrate
Review time…
11. What number represents a mole?
12. How many moles of He is 6.35 x 1026 particles of He?
13. When you see that magnesium has a mass number of 24.31;
what are the units we will be dealing with?
Answers
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Calcium iodide
Sodium nitrate
Iron (III) chloride or ferric chloride
Sulfur dioxide
Cobalt (II) fluoride trihydrate
Li3N
Al(OH)3
CBr4
Cu(NO2)2
Mg(C2H3O2)2∙2H2O
Answers
11. 6.022 x 1023
12. 1050 moles
13. grams / mole
The Molar Mass of Compounds
• To find the molar mass of a compound of two or more
elements, add the masses of 1 mol of each atom in the
compound's formula or formula unit.
• For example, to find the molar mass of CO2, count the
number of C and O atoms in the formula.
The Molar Mass of Compounds
• Then locate the molar mass of carbon and oxygen on the
periodic table.
• Add the molar masses of each carbon an oxygen that make
up the formula.
• CO2  1 C and 2 O  C = 12.01g/mol, O = 16.0g/mol, O =
16.0g/mol = 44.01 g/mol
• CO2  1C(12.01g/mol) + 2O(16.0g/mol) = 44.01 g/mol
The Molar Mass of Compounds
• You try…
• Calculate the molar mass of the ionic compound,
Ba(C2H3O2)2.
• Calculate the molar mass of ammonium sulfate.
Mole-Mass Conversions
Use molar mass
in g/mol
Mass
Percent
composition,
empirical and
molecular
formulas
Volume of
a solution
Number of
Number of
Moles
particles
Volume of a
gas at STP
Mole-Mass Conversions
• Molar mass can be used to convert between the mass of a
sample and the number of moles in that sample.
• If you know a sample’s mass, you can find the number of
moles in the sample.
• If you know how many moles are in a sample, you can find its
mass.
• Write the given number and unit as well as the formula for the
substance.
Mole-Mass Conversions
• Set up a factor label grid.
• Set up the conversion factor of grams per mole or moles per
gram depending on your initial given information.
• Use the atomic molar mass if converting atoms or use the
molecular molar mass if converting compounds.
• Write the answer with the correct units and the correct
number of significant digits.
Mole-Mass Conversions
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Example:
What is the molar mass of carbon dioxide?
How many molecules are in 1 dozen carbon monoxide?
How many molecules are in 1 mole of carbon dioxide?
How many moles are in 26.52g of CO2?
What is the mass in grams of 3.25 mol of NaBr?
Mini Quiz
1.
2.
3.
4.
5.
6.
7.
How many grams are in 1.00 mole of calcium phosphate?
How many grams are in 3.20 moles of calcium phosphate?
How many molecules are in 4.12 moles of calcium phosphate?
How many molecules are in 298.58g of calcium phosphate?
How many grams in 3.24 x 1025 molecules of calcium
phosphate?
What is the molarity of a solution that has 153.6g of Ca(NO3)2 in
1.2L of total solution?
How many liters does 402g of O2 gas take up at STP?
Objectives
• Define STP and standard molar volume
• Convert between gas volume, moles, mass and
number of particles
• Calculate the molarity of a solution
• Calculate the mass of solute
• Calculate the volume of a solution
Key Terms
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Atmosphere
Standard temperature and pressure (STP)
Standard molar volume
Concentrated
Dilute
Concentration
Molarity
Molar Volume
Volume of
a solution
Mass
Percent
composition,
empirical and
molecular
formulas
Number of
Number of
Moles
particles
Volume of a
gas at STP
Use 1 mole of a
gas at STP
takes up 22.4L
of space
Molar Volume
• Gases have a property that liquids and solids do not
have.
• Under certain conditions, 1 mol of any gas has a
volume of 22.4L.
• The two conditions that make this true are…
• A temperature of 0ºC
• A pressure of 1 atmosphere (atm)
Molar Volume
• Atmosphere (atm) is a unit for pressure.
• The air pressure at sea level is a bout 1 atm.
• The two conditions previously mentioned are
standard temperature and pressure (STP).
• For now it is important to know that 1 mol of any
gas at STP has a volume of 22.4L.
• This value is called standard molar volume.
Molar Volume
• For gases at STP, standard molar volume,
22.4L/mol, is used to convert between gas volume
and moles.
• This is a conversion factor that we can use in our
factor label grid.
• IMPORTANT: This conversion factor only works at
STP!
Molar Volume
• Example:
• What is the volume of 1.50 mol of CO2 @ STP?
• You try…
• How many moles are in 75.3L of O2 at STP?
Molarity Conversions
Volume of
a solution
Mass
Percent
composition,
empirical and
molecular
formulas
Use molarity
(M) in moles / L
Number of
Number of
Moles
particles
Volume of a
gas at STP
The Molarity of Solutions
• We discussed solutions in Unit 2.
• Solutions are homogenous mixtures.
• They consist of one or more solutes dissolved in a
solvent.
Concentration and Molarity
• Solutions can be concentrated or dilute, depending
on the amount of solute and solvent.
• A concentrated solution has more solute compared
to another solution with the same volume.
• A dilute solution has less solute compared to
another solution.
• Think of making a pitcher of pink lemonade.
• Mmmmmmmmmmmmmmmmmmm
Concentration and Molarity
• The directions state for you to add 4-1/3 cans of cold water
to the concentrate.
• If you add 3 cans of water to the concentrate, then the
lemonade will be very concentrated or strong.
• If you added 7 cans of water, the lemonade would be very
dilute or weak.
• Strong and weak, concentrated or dilute are qualitative
descriptions that are too vague for chemists to use so
chemists use different units to describe concentration.
Concentration and Molarity
• Chemists use units to measure concentration that
make the measurement quantitative.
• The units of solution concentration is called molarity
(M).
• Molarity is moles of solute / liters of entire solution
• The more moles of solute in a given amount of
solution, the more concentrated it is and the higher
the molarity.
Example
• The volume of an aqueous solution is 1.50L. It contains
12.5g of NaCl. What is the molarity of the solution?
• 12.5g NaCl is 0.241 moles NaCl
• 0.214 moles NaCl in 1.50L of solution is…
• 0.143M NaCl
• Practice…
• The volume of a solution is 1.67L. It contains 39.0g of
diatomic bromine. What is the molarity of the solution?
Today & This Week…
If you would like extra credit, the next few lines will be extremely important.
You can bring in a pumpkin and make it go “Boom!”
It must be carved and cleaned out—but leave the eyes, nose & mouth pieces in
place.
The first 2 people per class to answer my riddle get to bring one in.
Here is the deal…
I will not accept an answer today—guesses should be turned in no earlier than
tomorrow during brunch.
Mr. Habs is the middle man. You must give him your guess with your name,
hour, date, time and a spooky drawing.
Only one guess per student per day.
Oh yeah, quest is Thursday.
Here is the riddle…What do you get when you cross a vampire with a
snowman?
Mini Quiz
1. How many grams are in 3.20 moles of calcium
phosphate?
2. How many molecules are in 4.12 moles of calcium
phosphate?
3. How many molecules are in 298.58g of calcium
phosphate?
4. How many grams in 3.24 x 1025 molecules of calcium
phosphate?
5. What is the molarity of a solution that has 153.6g of
Ca(NO3)2 in 1.2L of total solution?
6. How many liters does 402g of O2 gas take up at STP?
More on Molarity
• The definition of molarity involves three factors,
moles/L, moles and liters.
• If you know any two of the three you can solve for the
third.
• Example…
• A 1.35M solution of KF has a volume of 1.33L. How
many moles of solute does it contain? How many
grams?
More on Molarity
• Another…
• An ammonium chloride solution has a concentration of
0.573M. It contains 0.323 mol of solute. What is the
volume of the solution?
Conversion Review
Sol’n
Volume
Use molarity in FL Grid
Mass
Molar
Mass in FL
Grid
Moles
Avogadro’s
#
Use 22.4L molar volume
at STP
Gas volume
@ STP
# of
particles
HW Problem
• How many moles of Cu are found in 155g of copper.
• The density of copper is 8.92 g/cm3. How many
atoms of copper are found in a sheet of copper that
measures 8 inches by 12 inches. Assume the sheet
is 2mm in thickness.
Today…
• Practice quiz…
• Notes % Composition and Empirical
Formula—pick up from desk.
• HW sheet for tonight (U have)
• Lesson 3/4 + HW sheet due tomorrow
• Thursday Quest—big one over lots of
stuff (20% old) - (80% new).
• Pumpkin Friday + lab?
• Extra Credit Winners—Tom,Pam & Alex
Objectives
•
1.
2.
3.
4.
5.
Get out your calculator, periodic table, sheet of paper and
flow chart for conversions (page 1 of this unit)
Convert 2.20 moles of sodium nitrate to grams—do not
ask anyone for the formula for nitrate.
Convert 350. grams of silver acetate to moles of silver
acetate—on your own.
How many molecules of sulfur dioxide are found in 11.7L
of this gas at STP?
How many moles of NaCl are contained in 255mL of
0.55M NaCl?
How many grams?
Objectives
• Find the total molar mass for each element in a
compound
• Find the percent composition of a compound
Percent Composition
• Compounds have a definite composition, given by
their formula and formula units.
• Water for example contains 2 atoms of H and 1
atom of O for every molecule of water.
• Each mole of water contains 2 moles of H and 2
moles of O for every mole of water.
• If we had exactly 1 mole of water there would be
2.02g of H and 16.0g of O.
• The total molar mass would be 18.02g.
Percent Composition
• This breakdown can be expressed as a percentage
called percent composition.
• Percent composition tells the percentage by mass
of each element in a compound.
• 2.02/18.02 for H = 11.2%
• 16.0/18.02 for O = 88.8%
• The two percentages add up to 100% or very close.
Percent Composition
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Try for carbon tetrafluodride
Try for calcium acetate.
SF6
NH3
Plumbous carbonate
Potassium nitrate
A compound has a molar mass of 42.4g/mol. It contains
elements X and Y. The total molar mass of element X is
6.9g/mol. What is the percentage of this compound?
• What is the percentage of the other?
Empirical and Molecular Formulas
• An empirical formula shows the smallest whole
number ratio of atoms in a compound.
• Sometimes an empirical formula is the compound’s
chemical formula.
• If it is not, the subscripts in the empirical formula are
important clues to the chemical formula.
Types of Formulas
• An example of an empirical formula is dextrose.
• For every 1 mol of C there are 2 mol of H and 1 mol of O.
• A molecule of dextrose always has 6 atoms of C, 12 atoms
of H and 6 atoms of O.
• C6H12O6 is the molecular formula of dextrose.
• A molecular formula gives the actual number of atoms in a
molecule.
• Molecular formulas is synonymous with chemical formula.
Types of Formulas
• Both ionic and molecular formulas have empirical
formulas.
• But only molecular compounds have molecular
formulas.
• Ionic compounds have formula units.
Types of Formulas
• An empirical formula shows the simplest ratio of
atoms in a compound.
• A molecular formula, or chemical formula, shows
the actual number of atoms in one molecule.
• A formula unit shows the simplest ratio of cations to
anions in an ionic compound.
Determining Empirical Formulas
• A mole ratio is a ratio or fraction that compares the
moles of one substance to the moles of another
substance.
• Mole ratio for water is 2 mol H : 1 mol O
Determining Empirical Formulas
• Steps:
1. Assume you have a 100g sample of the given compound. If you
know its % composition, you can change each percent symbol to
grams. Keep the number the same, for example, 30% becomes
30g.
• (if you are given a mass for each element, skip the first step)
2. For each element, convert grams to moles using molar mass. (treat
all elements as monatomic and remember sig figs).
3. Create a mole ratio using the mole amounts from step 2 by dividing
all mole components by the smallest number of moles.
4. The numbers in the simplest ratio of step 3 become the subscripts
for the chemical formula. Write the empirical formula using these
values.
BOO!
• We have the following to do for today…
• Finish notes (man there are a lot of notes!)
• Lab Day is pushed until Monday  so that means that
Quest day is now pushed back to Weds !
• After notes we can say Whoa! With a fiery pumpkin face!
Determining Empirical Formulas
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Example:
What is the empirical formula of an unknown substance
that contains 30.4% nitrogen and 69.6% oxygen by mass?
What is the empirical formula of a compound that contains
80.0% carbon and 20.0% hydrogen by mass?
What is the empirical formula of a molecular compound
that contains 4.37g of phosphorus and 5.63g of oxygen?
A compound contains 4.20g of carbon and 4.21 x 1023
atoms of hydrogen and 1.05 mole of oxygen. What is the
empirical formula of this compound?
Molecular Formulas and Hydrates
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A molecular formula is either the empirical formula or a
multiple of the empirical formula.
molecular formula = n (empirical formula)
n must be a whole number.
For the compound dextrose, n = 6.
Empirical formula = CH2O
Molecular formula = C6H12O6 = 6 (CH2O)
Ex credit Q for the Quest…are dextrose and glucose the
same thing? If not, how can they have the same molecular
formula?
Determining Molecular Formulas
• To find the molecular formula of a compound, you
must know two things…
• the empirical formula
• the molar mass of the compound
• Think of dextrose again for example.
• Suppose you do not know its molecular formula,
but you know its empirical formula and that the
mass of 1 mol of dextrose is 180.0 g/mol.
Determining Molecular Formulas
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Calculate the mass of the empirical formula—this is not necessarily
the molar mass of the compound.
For dextrose…
12.01g/mol + 2(1.01 g/mol) + 16.0 g/mol =
30.02 g/mol
Set up the following…
Molar mass of compound = n (empirical formula mass)
180.0 g/mol = n (30.02 g/mol)
n=6
So multiply the subscripts of the empirical formula by 6 to get…
C6H12O6
Examples
•
•
•
•
The empirical formula of a compound is NO2. The molar
mass of the compound is 92.0 g/mol. What is the
molecular formula?
The empirical formula of a compound is CH. The molar
mass of the compound is 78.0 g/mol. What is the
molecular formula?
An unknown compound contains 2.17g of C, 0.362g of H
and 0.966g of oxygen. Its molar mass is 116.0 g/mol. What
are its empirical and molecular formulas?
An unknown compound contains 21.8g of phosphorus and
28.2g of O. Its molar mass is 284 g/mol. What are its
empirical and molecular formulas?
Hydrates
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•
•
•
Some compounds have molecules of water trapped as
part of the compound.
Hydrates are compounds that are chemically combined
with water in a specific ratio.
The compound in a hydrate is usually on ionic compound.
In a hydrate’s empirical formula, the water molecules are
written a the end.
For example, Ni(NO3)2· 6H2O shows that there are 6 water
molecules with each formula unit of nickel (II) nitrate.
The dot in the formula is NOT a multiplication sign.
Hydrates
• On a larger scale this tells us that there are 6
moles of water molecules for every mole of nickel
(II) nitrate.
• When a hydrate is heated, the water molecules
leave and mix with the surrounding air.
• What remains after heating is the ionic compound
without the water.
• Its formula unit shows no water molecules.
• CuSO4·5H2O + heat  CuSO4
Hydrates
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•
Suppose you measure the mass of a sample of hydrate.
Then you heat it until the water is gone.
You measure the mass of the compound that is left.
You know the following:
Mass of hydrate
Mass of compound without water
Mass of water in sample (hydrate mass – compound
mass)
Hydrates
• From this information, you can find the empirical
formula of the hydrate.
• It is based on the ratio of moles of the compound to
moles of water.
Example
• A hydrate of magnesium sulfate is heated with the
following results. What is the empirical formula of
the hydrate?
• Mass of hydrate before heating = 5.65g
• Mass of compound after heating = 2.76g
Example
• A hydrate of sodium sulfide is heated with the
following results. What is the empirical formula of
the hydrate?
• Mass of hydrate before heating = 154g
• Mass of compound after heating = 50. g
Physics
• Sit down in quest seats and read the following…
• Be silent during prayer and announcements—if you talk, you cannot
work on the quest 
• Today’s Quest—you have the class period to finish it—but you cannot
ask me any questions whatsoever.
• Calculator, equation sheet (not sheets) can be on your desk.
• This is the last grade for this 1st MP.
• There will be big changes on Monday…