Chapter 10 – CHEMICAL QUANTITIES
The MOLE
Avogadro’s Hypothesis
Equal volumes of gases (@ same T and p) have the same #
molecules.
The number of 12C atoms in
12.00 grams of carbon is called
Avogadro’s Number = 6.02(10)23
This quantity is called a MOLE
(Just as a dozen = 12)
1 mole = 6.02(10)23 particles
[“atoms”/”molecules”/”formula units”]
___________________________________
STP: Standard
At STP... 1
Temperature and Pressure
0o C
1 atm
mole = 22.4 L for any gas.
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 1
gram atomic mass
gram molecular mass
gram formula mass
-
MOLAR MASS of atoms
-
MOLAR MASS of molecules
-
MOLAR MASS of ionic cmpd.
MOLAR MASS:
The mass of one mole of a substance.
It is found by adding the molar masses of
each individual element proportionally
(using the Periodic Table as a reference).
Ex:
Atom or
Molecule or
Formula Unit
Atomic or
Molecular or Molar
Formula Mass Mass
He
1(4.0) = 4.0 amu
4.0 g
O2
2(16.0) = 32.0 amu
32.0 g
2(1.0) + (16.0) = 18.0 amu
18.0 g
(24.3) + 2(35.5) = 95.3 amu
95.3 g
(40.1)+2(14.0)+6(16.0)= 164.1 amu
164.1g
H2O
MgCl2
Ca(NO3)2
1 mole = [Periodic Table] g
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 2
1 mole = 6.02(10)23 particles
1 mole = [Periodic Table] grams
1 mole = 22.4 L of gas @ STP
Practice:
1.5 mol CO2  L CO2 (@STP)
1.5 mol CO2  grams CO2
1.5 mol CO2  molecules CO2
11.2 L CO2 (@STP) g CO2
110. g CO2  molecules CO2
2.00(10)23 molecules CO2  L CO2 (@STP)
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 3
% Composition is by MASS (Grams)
Ex. Finding % Composition
from empirical formula
methane
carbon
hydrogen
CH4
mass C =
mass CH4
12.0 g x 100
16.0 g
=
75.0% C
mass H =
mass CH4
4.0 g x 100
16.0 g
=
25.0 % H
Empirical formula is by MOLES
Ex. Find empirical formula of a compound that is
75.0% C and 25.0% H by mass.
Assume 100.0 grams of the compound:
75.0 g C x 1 mol = 6.25 mol C  1
12.0 g
25.0 g H x 1 mol
1.0 g
=
25.0 mol H  4
 CH4
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 4
Molecular Formulas
“Simplest”
Empirical Formula
“Real Life”
Molecular Formula
Hydrates: Composed of a salt and water
CuSO4•5H2O
mass of Salt + mass of H2O = mass of hydrate
Find % H2O
Find grams of water in a 8.88 g sample of CuSO4•5H2O
Find Empirical Formula of hydrate from sample data
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 5
ws – Molar Mass
Formula
Molar Mass Sol In- Name
sol
1 NaCl
2 CaBr2
3 K2SO4
4 Mg(NO3)2
5 KMnO4
6 CuSO4•5H2O
7 Na2CrO4
8 LiBrO3
9 Zn3(PO4)2•4H2O
10 Mg3(PO4)2
11 MgSO4•7H2O
12 (NH4)2SO4
13 Cu(OH)2
14 CaCO3
15 NaOH
16 NH4Cl
17 KCl
18 K3PO4
19 NH4OH
20 Ba(C2H3O2)2
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 6
ws – Moles and Particles (using Avogadro’s Number)
1. How many molecules are in 3.5 moles H2O?
2. How many atoms are in 1.5 moles of Ne?
3. How many formula units are in 2.25 moles of NaCl?
4. How many molecules are in 0.50 moles of C6H12O6?
5. How many moles are in 3.01(10)23 molecules of H2O?
6. How many moles are in 3.01(10)23 atoms of Ne?
7. How many moles are in 9.03(10)23 formula units of NaCl?
8. How many moles are in 2.01(10)24 molecules of C6H12O6?
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 7
ws – Moles and Mass (Using the Periodic Table)
1. How many grams are in 3.5 moles H2O?
2. How many grams are in 1.5 moles of Ne?
3. How many grams are in 2.25 moles of NaCl?
4. How many grams are in 0.50 moles of C6H12O6?
5. How many moles are in 75.0 grams of H2O?
6. How many moles are in 75.0 grams of Ne?
7. How many moles are in 50.0 grams of NaCl?
8. How many moles are in 50.0 grams of C6H12O6?
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 8
ws – Moles and Volume (Using Molar Volume)
1. How many Liters are in 3.5 moles SO2(g) @ STP?
2. How many Liters are in 1.5 moles of Ne(g) @STP?
3. How many Liters are in 2.25 moles of CO2(g) @STP?
4. How many Liters are in 0.50 moles of SO2(g) @STP?
5. How many moles are in 75.0 L SO2(g) @ STP?
6. How many moles are in 75.0 L of Ne(g) @STP?
7. How many moles are in 135 L of CO2(g) @STP?
8. How many moles are in 49.0 L of SO2(g) @STP?
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 9
ws – Mixed Mole Problems
1. How many Liters are in 32.0 g of SO2(g) @ STP?
2. How many grams are in 1.50(10)24 atoms of Ne?
3. How many molecules are in 53.0 L of CO2(g) @STP?
4. How many Liters are in 8.75(10)23 molecules of SO2(g) @STP?
5. How many grams are in 75.0 L SO2(g) @ STP?
6. How many atoms are in 75.0 g of Ne?
7. How many grams are in 135 L of CO2(g) @STP?
8. How many molecules are in 49.0 L of SO2(g) @STP?
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 10
ws – Mole Conversions
Directions: Perform the following conversions using the appropriate conversion factors.
NOTE: (g) after a formula means “gas.”
* designates more than one step may be required.
1.
4.50 mol O2  g O2
2.
4.50 mol O2(g) L O2(g) @STP
3.
91.0 g N2 mol N2
4.
2.75 mol CH4 # molecules
5.
2.75 mol CH4 g CH4
6.
2.75 mol CH4(g) L CH4(g) @STP
*7. 110. g CO2(g) L CO2(g) @STP
*8. 110. g CO2 # molecules
*9. 3.01(10)23 molecules H2O g H2O
*10. 100.8 L SO2(g) @STP g SO2(g)
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 11
ws – Percent Composition
Directions: Find the % composition for each of the following compounds and refer to #1-5
to answer #6-8.
1. H2O
H= ____________ O = ____________
2. MgCl2
Mg= ____________ Cl = ____________
3. Ca(NO3)2
Ca= ____________ N= ____________ O= ____________
4. (NH4)3PO4
N= ____________ H= ____________ P= ____________ O= ____________
5. Al2(CO3)3
Al= ____________ C= ____________ O= ____________
6. How many grams of oxygen can be produced from the decomposition
of 60.0 g of H2O?
7. What mass of magnesium is in 75.0 g of MgCl2?
8. What mass of carbon is necessary to make 38.0 g of Al2(CO3)3?
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 12
ws - Hydrates and % H2O
Directions: Name each hydrate and find the % water (by mass) in each.
% H2O
Name
1. Na2SO4•10H2O
2. MgSO4•7H2O
3. CaCl2•2H2O
4. FeSO4•7H2O
5. CoCl2•2H2O
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 13
ws – Composition of Hydrates
1. What is the percentage of water in Na2S•9H2O?
2. If you heated 7.7 g of Na2S•9H2O, how much water would be driven off?
3. What is the percentage of water in Na2CO3•H2O?
4. If you heated 5.00 g of Na2CO3•H2O, how much salt would remain?
5. An 8.00 g sample of BaCl2 was heated, and only 6.88 g of the anhydrous
salt remained. What is the percentage of water in the hydrate?
6. A 12.0 g sample of Cu(NO3)2 •nH2O was heated and 9.36 g of the
anhydrous salt remained. What is the value of n?
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 14
ws - Hydrate Empirical Formulas
Directions: Find the percentage of water, empirical formula, and name for each hydrate below using
the experimental data given for problems #1-3.
1. A hydrate of CuSO4 was found to be composed of 12.76 g of copper sulfate and 7.200 g of water.
% H2O = ______________
Empirical Formula = ___________________
Name = ______________________________
2. A hydrate of sulfuric acid (H2SO4) had a mass of 3.48 g before heating. After heating the salt
had a mass of 2.94 g.
% H2O = ______________
Empirical Formula = ___________________
Name = _____________________________________
3. A hydrate of barium hydroxide (Ba(OH)2) had a total mass of 14.19 g before heating. After
heating 6.48 grams of water were driven off.
% H2O = ______________
Empirical Formula = ___________________
Name = ______________________________
*4. A sample of sodium sulfate decahydrate was heated and the resulting salt remaining was 0.142
grams. How many grams of water must have been driven off?
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 15
ws – Determining Empirical Formulas
1. 11.1% hydrogen, 88.9% oxygen
2. 39.3 % sodium, 60.7% chlorine
3. 32.4% sodium, 22.6% sulfur, 45.0% oxygen
4. 22.1% aluminum, 25.4% phosphorus, 52.5% oxygen
5. 56.6% potassium, 8.68% carbon, 34.7% oxygen
6. 25.3% copper, 12.9% sulfur, 25.7% oxygen, 36.1% water
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 16
ws – Determining Molecular Formulas
1. A compound has an empirical formula of NH2. Its gram molecular mass is
32.0 g/mol. What is its molecular formula?
2. The empirical formula of a compound is CH2. Its molar mass is 42.0 g/mol.
What is its molecular formula?
3. A compound is found to be 40.0% carbon, 6.67% hydrogen, and 53.3%
oxygen. Its molar mass is 180.0 g/mol. What is its molecular formula?
4. A compound has 40.0% carbon, 6.67% hydrogen, and 53.3% oxygen. It has
a molar mass of 120.0 g/mol. Find its molecular formula.
5. A compound has 29.1% sodium, 40.6% sulfur, and 30.3% oxygen. What is
its molecular formula if has a molar mass of 158.2 g/mol?
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 17
Experiment: Finding % Sugar in Gum (Rough Copy)
Name:____________________________________ Date: ______________________ Period: ______
Purpose:
Materials:
Procedure:
Data:
Brand of Gum
________________
Mass of Gum before chewing
_________
____
Mass of Gum after chewing
_________
____
Calculations: Show your work!
Find the mass of sugar in the Gum
_________
____
Find the % sugar in the Gum
_________
____
Conclusion:
Mention
your result
what assumption you made in this lab
which Gum in the class was the highest % sugar
which was the lowest % sugar
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 18
Experiment: Finding % Sugar in Gum (Final Copy)
Name:____________________________________ Date: ______________________ Period: ______
Purpose:
Materials:
Procedure:
Data:
Brand of Gum
________________
Mass of Gum before chewing
_________
____
Mass of Gum after chewing
_________
____
Calculations: Show your work!
Find the mass of sugar in the Gum
_________
____
Find the % sugar in the Gum
_________
____
Conclusion:
CHEMISTRY – Chapter 10 – Scotch Plains-Fanwood High School
Page 19