BCLN CHEMISTRY 11 - Rev. Mar/2016
Unit 4 ~ Learning Guide Name: ______________________________
Instructions:
Using a pencil, complete the following notes as you work through the related lessons. Show ALL
work as is explained in the lessons. You are required to have this package completed BEFORE
you write your unit test. Do your best and ask questions if you don’t understand anything!
The Mole:
1. What is the definition of a mole? Note that you may also see this term written as mol.
.
2. What is the value of a mole?
3. How would you enter this number into your calculator?
Avogadro's Number:
1. Fill in the symbols for the following terms
Term
Symbol
Avagadro's Number
mole
Number of Particles
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BCLN CHEMISTRY 11 - Rev. Mar/2016
Mole Calculations:
Show your work for all of these questions. Remember to ensure units cancel properly while doing unit
conversions. Hint: If you are ever getting an answer with powers in the 40s then you have a unit
conversion upside down!
1. How many grams are there in 2.3 moles of sulfur?
2. How many grams are there in 5.15 moles of mercury?
3. How many moles are there in 47 grams of iron?
4. How many moles are there in 215 grams of copper?
5. How many atoms are there in 5.2 moles of zinc?
6. How many atoms are there in 31.6 moles of magnesium?
7. How many moles are there in 7.5x1025 atoms of xenon?
8. How many moles are there in 3.22x1024 atoms of potassium?
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BCLN CHEMISTRY 11 - Rev. Mar/2016
9. How many atoms are there in 37.5g of aluminum?
10. How many grams are there in 5.2 x 1015 atoms of manganese?
Molar Mass and Compounds:
1. Determine the molar mass of the following compounds. Show your work in the box provided.
Remember to provide the correct units in your final answer.
Formula
Work
Molar Mass
FeS
Ni2O3
C12H22O11
(NH4)3PO4
Mn(MnO4)4
2. What do we use to convert between grams and moles?
3. Particles is one of the overall term for atoms and molecules. You may also see the term formula
units used when dealing with ionic compounds. What do we use to convert between moles and
particles?
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BCLN CHEMISTRY 11 - Rev. Mar/2016
4. How many molecules of MgCl2 are in 205 g of MgCl2?
5. How many atoms of hydrogen are there in 25.3g of CH4. Note this will require THREE unit
conversions to answer correctly!
6. How many oxygen atoms are there in 98.4g of oxygen gas. Hint: oxygen gas just might be
diatomic! Be warned that on a test you will NOT be told if an element is diatomic. You need to
memorize the diatomic elements.
7. If a sample of Fe2S3 contains 1.25x1015 iron atoms what is the mass in grams?
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BCLN CHEMISTRY 11 - Rev. Mar/2016
Characteristics & Molar Volume of Gases:
1. What does STP stand for?
2. What is the main difference between STP and SATP? Please don't say the A!
3. What is the molar volume at STP and SATP? Be sure to include the correct units. Note that these
values are on your data table so you do NOT need to memorize them.
4. What volume in litres does 27.3 g of argon gas occupy at STP?
5. What volume in litres does 85.4 g of nitrogen gas occupy at SATP?
6. How many moles of bromine gas are there in a volume of 80.0L at STP?
7. How many atoms of hydrogen are there in 129 L of ethane gas (C2H6) at SATP?
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BCLN CHEMISTRY 11 - Rev. Mar/2016
Percent Composition:
1. What is the definition of percent composition?
2. What is the percent composition of each element in SiCl4?
3. What is the percent composition of each element in Ca(BrO3)2?
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BCLN CHEMISTRY 11 - Rev. Mar/2016
Empirical Formula:
1. What are the 3 steps to determining an empirical formula given the percent composition of
compound?
2. A compound is found by analysis to be by mass 79.85% carbon and 20.15% hydrogen. What is its
empirical formula?
3. A compound is found by analysis to be by mass 24.4% calcium, 17.1% nitrogen and 58.5%
oxygen. What is its empirical formula?
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BCLN CHEMISTRY 11 - Rev. Mar/2016
4. The empirical formula of a substance indicates the simplest whole number ratios of the different
kinds of atoms that make up the substance. The empirical formula of a substance with the molecular
formula N2O4, for example. is NO2. Fill in the table with the empirical formula for each of the
following hydrocarbon compounds.
Compound Name
Molecular Formula
methane
CH4
benzene
C6H6
ethane
C2H6
ethylene (ethane)
C2H4
octane
C8H18
acetylene (ethyne)
C2H2
Naphthalene
C10H8
Empirical Formula
5. After substantial heating, 0.476g of uranium produced 0.524 g of a compound with oxygen.
Determine the empirical formula. Hint: you will need to subtract those 2 numbers to get a mass of
oxygen to work with.
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BCLN CHEMISTRY 11 - Rev. Mar/2016
Molecular Formula:
1. What is the difference between a molecular formula and an empirical formula?
2. The empirical formula of a compound is CH3. Its molar mass is 30.08 g/mole. What is its
molecular formula?
3. A compound has the following percentage mass composition: 71.35% carbon, 12.00% hydrogen,
and 16.65% nitrogen. Its molar mass is 252.48 g/mole. Determine its molecular formula.
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BCLN CHEMISTRY 11 - Rev. Mar/2016
Molar Concentration (Molarity):
1. What is the difference between a solute and a solvent?
2. If 33.7 moles of MgCl2 is dissolved to make 8.3L of solution, what is the molarity of the solution?
3. If 275.2g of KMnO4 is dissolved in to make 0.500 L of solution, what is the molar concentration
of the solution?
4. 205 L of carbon dioxide gas at STP is compressed and then dissolved in 10.0 L of water. What is
the molar concentration of the resulting solution?
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BCLN CHEMISTRY 11 - Rev. Mar/2016
Solutions and Dilutions:
1. Why is a volumetric flask much better than a beaker for preparing solutions with accurate known
concentrations?
2. If [K3PO4 ] = 0.250 M, how many grams of K3PO4 are in 750.0 mL of solution? Remember that
M is the same as mol/L.
3. What volume in mL of 0.600 M aluminum sulfate solution can be prepared using 35.00 grams of
aluminum sulfate ? Hint: Remember you need to balance aluminum and sulfate to create the
correct chemical formula
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BCLN CHEMISTRY 11 - Rev. Mar/2016
4. What is the resulting concentration of BaBr2(aq) when 400. mL of water are added to 375. mL of
0.350 M BaBr2 (aq) ?
5. How much water needs to be added to 15.0 mL of a concentrated solution of HCl(aq) to lower it's
concentration to 1.00 M? Note: concentrated HCl(aq) is 11.6 M
Answers:
The Mole
1. 74 g S
2. 1030 g Hg or 1.030x103 g Hg
5. 3.1 x 1024 atoms Zn 6. 1.90 x 1025 atoms Mg
8. 5.34 mol K
9. 8.37 x 1023 atoms Al
3. 0.84 mol Fe
7. 125 mol Xe
10. 4.7 x 10-7 g Mn
Molar Mass and Compounds
1. 87.91 g/mol, 165.38 g/mol, 342.34 g/mol, 149.12 g/mol, 530.68 g/mol
4. 1.30x1024 molecules MgCl2
5. 3.80x1024 atoms H
6. 3.70x1024 atoms O
7. 2.16x10-7 g Fe2S3
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4. 3.38 mol Cu
BCLN CHEMISTRY 11 - Rev. Mar/2016
Characteristics & Molar Volume of Gases
4. 15.3 L Ar
5. 75.6 L N2
6. 3.57 mol Br2
7. 1.89x1025 atoms H
Percent Composition
2. %Si = 16.53%
%Cl = 83.47%
3. %Ca = 13.55%
%Br = 54.01%
%O = 32.45%
Empirical Formula
2. CH3
3. CaN2O6
5. U2O3
Molecular Formula
2. C2H6
3. C15H30N3
Molar Concentration
2. [MgCl2] = 4.1 M
3. [KMnO4] = 3.48 M
4. [CO2] = 0.915 M
3. 170. mL Al2(SO4)3
4. [Final] = 0.169 M
Solutions and Dilutions
2. 39.8 g K3PO4
5. Water added = 159 mL
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