CHEMISTRY 11/20
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.
A unit measuring very large amounts of very small things like atoms and moleculues
2. What is the value of a mole?
the exact value of one mol is 6.02214076 × 10^23
3. How would you enter this number into your calculator?
6.02214076 multiply by 10^23
Avogadro's Number:
1. Fill in the symbols for the following terms
Term
Avagadro's Number
mole
Number of Particles
2020-11-18
Symbol
N
A
Mol
N
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CHEMISTRY 11/20
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! There are hints for these in the answer key but you should try them on your own first! This
will be true for the rest of the sections in this learning guide as well.
1. How many grams are there in 2.3 moles of sulfur?
2.3 mol x 32.065 u = 73.7495g
2. How many grams are there in 5.15 moles of mercury?
5.15 mol x 200.59 u = 1 033.0385g
3. How many moles are there in 47 grams of iron?
47g/55.845u = 0.8641mol
4. How many moles are there in 215 grams of copper?
215/63.546 u = 3.3833 mol
5. How many atoms are there in 5.2 moles of zinc?
atoms =1.1149668e+23
atoms = 6.022×10^23/28.0855 ×5.2
6. How many atoms are there in 31.6 moles of magnesium?
atoms = 6.022x10^23/24.305 x 31.6 = 7.8294672e+23
7. How many moles are there in 7.50x1025 atoms of xenon?
(7.50 x 10^25 atoms) / (6.022 x 10^23 atoms/mol) = 125 mol
8. How many moles are there in 3.22x1024 atoms of potassium?
3.22x10^24 atoms / 6.022 x 10^23 atoms/mol = 5.34 mol
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CHEMISTRY 11/20
9. How many atoms are there in 37.5g of aluminum?
37.5/27 ×6.022×10^23 =8.363×10^23
10. How many grams are there in 5.2 x 1015 atoms of manganese?
54.93804 grams
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
FeS
Ni2O3
Work
Molar Mass
55.845 + 32.065 =87.91g/mol
Fe
S
87.91g/mol
58.6934*2 + 15.9994*3 = 165.385 g/mol
Ni
C12H22O11
(NH4)3PO4
Mn(MnO4)4
12.0107*12 + 1.00794*22 + 15.9994*11 =
342.29648 g/mol
(14.0067 + 1.00794*4)*3 + 30.973761 + 15.9994*4
54.938049 + (54.938049 + 15.9994*4)*4
2. What do we use to convert between grams and moles?
Multiply moles by molar mass and vice versa
2020-11-18
165.385 g/mol
O
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342.29648 g/mol
149.086741 g/mol
530.680645 g/mol
CHEMISTRY 11/20
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?
Multiplying or dividing by Avogardo's number
4. How many molecules of MgCl2 are in 205 g of MgCl2?
205/95.211 = 2.15311 mol
2.15311 mol x 6.022 x 10^23 = 1.29660284 × 10^24 molecules
5. How many atoms of hydrogen are there in 25.3g of CH4. Note this will require THREE unit
conversions to answer correctly!
I got stuck on this one
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.
3.702×10^24 atoms of Oxygen.
7. If a sample of Fe2S3 contains 1.25x1015 iron atoms what is the mass in grams?
4.31 x 10^-7
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CHEMISTRY 11/20
Characteristics & Molar Volume of Gases:
1. What does STP stand for?
STP stands for Standard Temperature and Pressure
2. What is the main difference between STP and SATP? Please don't say the A!
STP is good for calculations, but isnt practical in real settings since most environments are room
temperature and not 0 degrees celsius
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.
22.4 L for 1 mole of any ideal gas at a temperature equal to 273.15 K and a pressure equal to 1.00 atm
4. What volume in litres does 27.3 g of argon gas occupy at STP?
15.3L Argon
5.
in in
litres
doesdoes
85.485.4
g of nitrogen
gas occupy
at SATP?
5. What
Whatvolume
volume
litres
g of nitrogen
gas occupy
at SATP?
75.6L N2
6.
of bromine
gas are
in a volume
of 80.0Lofat80.0L
STP? at STP?
6. How
Howmany
manymoles
moles
of bromine
gasthere
are there
in a volume
3.57 mol Br2
7. How many atoms of hydrogen are there in 129 L of ethane gas (C2H6) at SATP?
1.88x10^25 atoms H
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CHEMISTRY 11/20
Molar Concentration (Molarity):
1. What is the difference between a solute and a solvent?
A solvent does the dissolving while the solute is the thing thats being dissolved into the solution
2. If 33.7 moles of MgCl2 is dissolved to make 8.3L of solution, what is the molarity of the solution?
MgCl2 = 4.1M
3. If 275.2g of KMnO4 is dissolved in to make 0.500 L of solution, what is the molar concentration
of the solution?
KMnO4 = 3.48M
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?
CO2 = 0.915 M
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Solutions and Dilutions:
1. Why is a volumetric flask much better than a beaker for preparing solutions with accurate known
concentrations?
Volumetric flasks are calibrated while beakers are not so they are less precise
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.
39.8 g K3PO4
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
170 mL Al2(SO4)3
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CHEMISTRY 11/20
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) ?
0.169 M
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? [concentrated HCl(aq)] =11.6 M.
159 mL of water needs to be added
Answers:
Mole Calculations Hints: This is the layout you need to solve these questions. Notice that the
units always cancel!
()
( 0(
1. ___mol S x ____*+, ) =
3. ___ g Fe x
*+, 34
___ ( 34
5. ___ mol Zn x
2. ___ mol Hg x ___*+, 0( =
*+, 78
=
;<+*= >?
___ *+, >?
4. ___ g Cu x ___ ( 78 =
=
6. ___ mol Mg x
*+, F4
7. ___ atoms Xe x ___ ;<+*= F4 =
*+, J,
9. ___ g Al x ___ ( J, x
2020-11-18
___ ;<+*= J,
K *+, J,
=
;<+*= A(
___ *+, A(
=
*+, F4
8. ___ atoms K x ___ ;<+*= H =
*+, A?
( A?
10. ___ atoms Mn x ___ ;<+*= A? x ___ *+, A? =
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CHEMISTRY 11/20
Mole Calculations Answers:
2. 1030 g S or 1.030x103 g Hg 3. 0.84 mol Fe
1. 74 g S
5. 3.1 x 1024 atoms Zn 6. 1.90 x 1025 atoms Mg
7. 125 mol Zn
9. 8.37 x 1023 atoms Al
8. 5.35 mol K
4. 3.38 mol Cu
10. 4.7 x 10-7 g Mn
Molar Mass and Compounds Hints: This is the layout you need to solve these questions. Notice
that the units always cancel!
4. ___ g MgClL x
*+, A(7,M
___ ( A(7,M
*+, 70P
5. ___ CHO x
___ 70P
*+, RM
6. ___ g OL x
___ ( RM
*+,4N8,4= A(7,M
x
*+,4N8,4= 70P
x
___ *+, 70P
*+,4N8,4= RM
x
___ *+, RM
*+,4N8,4 34M )S
7. ___ atoms Fe x
=
___ *+, A(7,M
___ ;<+*= 34
;<+*= 0
x ___ *+,4N8,4 70 =
P
;<+*= R
x ___ *+,4N8,4 R =
M
*+, 34 )
x ___ *+,4N8,4M 34S
M )S
( 34 )
M S
x ___ *+, 34
=
)
M S
Molar Mass and Compounds Answers:
1. 87.91 g/mol, 165.38 g/mol, 342.34 g/mol, 149.12 g/mol, 530.70 g/mol
4. 1.30x10
1.30x1024 molecules MgCl2
5. 3.80x1024 atoms H
6. 3.70x1024 atoms O
7. 2.16x10-7 g Fe2S3
Characteristics & Molar Volume of Gases Hints: This is the layout you need to solve these
questions. Notice that the units always cancel!
4. ___ Ar x
*+, JU
___ ( JU
6. ___ BrL x
*+, YUM
___ V YUM
7. ___ CL HZ x
V JU
x ___ *+, JU =
*+, WM
5. ___ x
___ ( WM
VW
x ___ *+,MW =
M
=
*+, 7M 0[
___ 7M 0[
x
*+,4N8,4= 7M 0[
___ *+, 7M 0[
;<+*= 0
x ___ *+,4N8,4 7
M 0[
=
Characteristics & Molar Volume of Gases Answers:
4. 15.3 L Ar
5. 75.6 L N2
6. 3.57 mol Br2
7. 1.88x1025 atoms H
Molar Concentration Answers:
2. [MgCl2] = 4.1 M
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3. [KMnO4] = 3.48 M
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4. [CO2] = 0.915 M
CHEMISTRY 11/20
Solutions and Dilutions Hints:
2. ___ mL K ] POO x
V HS_RP
___ *V HS_RP
3. ___ g AlL (SOO )] x
x
*+, J,M ()RP )S
___ ( J,M ()RP)S
*+, HS _RP
___ V HS_RP
x ___
( HS_RP
*+, HS _RP
V J, ()RP)S
M
x ___ *+, J,
M ()RP)S
x
=
*V J,M ()RP)S
___ V J,M ()RP)S
4 and 5. Remember that: [Final] x Final Volume = [Initial] x Initial Volume
Solutions and Dilutions Answers:
2. 39.8 g K3PO4
3. 170. mL Al2(SO4)3
4. 0.169 M
5. Water added = 159 mL
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4. [Final] = 0.169 M