Chemistry SOL Review by Anne Mooring (Jamestown High School, Williamsburg VA, 2006)

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Chemistry SOL Reviewby Anne Mooring (Jamestown
High School, Williamsburg VA, 2006)

• Part 4 Molar Relationships
• The mole and molar calculations
• Stoichiometry
• Gas Laws (Boyle, Charles, Combined, Ideal,
  Dalton, Graham)
• Solution Concentrations
• Chemical Equilibrium
• Acid/Base Theory
• Use the SOL periodic table. Click here for link

You will need a calculator and periodic table to
complete this section.
This section represents 8/50 of the SOL questions
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Chemistry SOL Review Molar Relationships
The Mole and Mole Calculations
One mole 6.02 x 1023 representative
particles One mole 22.4 Liters of gas at 0C
and one atmosphere of pressure One mole the
atomic mass listed on the periodic table. For
example one mole of Helium contains 6.02 x 1023
atoms of Helium and it has a mass of 4.00260
grams. At 0C and one atmosphere of pressure, it
would occupy 22.4 Liters.
Sample problem How many liters would 2.0 moles
of Neon occupy? Answer 2.0 moles Ne x 22.4
Liters Ne 44.8 Liters Ne 1.0 moles Ne
Sample problem How many moles are in 15.2 grams
of Lithium? Answer 15.2 g Li x 1 mole Li
2.19 mole Li 6.941 g Li
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Chemistry SOL Review Molar Relationships
The Mole and Mole Calculations
One mole 6.02 x 1023 representative
particles One mole 22.4 Liters of gas at 0C
and one atmosphere of pressure One mole the
atomic mass listed on the periodic table.
Sample problem How many liters would 14 grams
of Helium occupy? Answer 14 g He x 1 mole
He x 22.4 L He 78 Liters He
4.0026 g He 1 mole He
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Chemistry SOL Review Molar Relationships
The Mole and Mole Calculations
One mole 6.02 x 1023 representative
particles One mole 22.4 Liters of gas at 0C
and one atmosphere of pressure One mole the
atomic mass listed on the periodic table. You
try one
What is the mass of 9.0 Liters of Argon gas at
0C and one atmosphere of pressure?
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Chemistry SOL Review Molar Relationships
The Mole and Mole Calculations
One mole 6.02 x 1023 representative
particles One mole 22.4 Liters of gas at 0C
and one atmosphere of pressure One mole the
atomic mass listed on the periodic table. You
try one
What is the mass of 9.0 Liters of Argon gas at
0C and one atmosphere of pressure? 9.0 L Ar x
1 mol Ar x 39.948 g Ar 16 g Ar
22.4 L Ar 1 mole Ar
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Chemistry SOL Review Molar Relationships
The Mole and Mole Calculations
The molar mass the sum of all the atomic
masses. Example Ca(NO3)2 40.08 2(14.01)
6(16.00) 164.10 grams You try one What is
the gram formula mass (molar mass) of Mg3(PO4)2?
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Chemistry SOL Review Molar Relationships
The Mole and Mole Calculations
The molar mass the sum of all the atomic
masses. Example Ca(NO3)2 40.08 2(14.01)
6(16.00) 164.10 grams You try one What is the
gram formula mass (molar mass) of
Mg3(PO4)2? 3(24.305) 2(30.97376) 8(15.9994)
262.86 grams
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Chemistry SOL Review Molar Relationships
The Mole and Mole Calculations
The molar mass the sum of all the atomic
masses. Example Ca(NO3)2 40.08 2(14.01)
6(16.00) 164.10 grams You try one What is the
gram formula mass (molar mass) of
Mg3(PO4)2? 3(24.305) 2(30.97376) 8(15.9994)
262.86 grams What is the percent Magnesium in
Mg3(PO4)2? Answer 3(24.305) x 100 27.7
262.86 You try one What is the
percent Lithium in Li2SiO3? molar mass 2(6.941)
28.0855 3(15.9994) 89.9657 g Li
2(6.941) x 100 15.4 89.9657
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Chemistry SOL Review Molar Relationships
A Brief Return to Empirical Formulas
Empirical Formulas are the reduced form of
Molecular formulas. For example The empirical
formula for C5H10 is CH2. A favorite SOL type
question What is the empirical formula of a
compound that contains 30 Nitrogen and 70
Oxygen?
This is really a percent composition problem.
Figure out which compound contains 30 nitrogen.
a) N2O b) NO2 c) N2O5 d) NO
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Chemistry SOL Review Molar Relationships
The Mole and Mole Calculations
At Standard Temperature and Pressure (STP) 1 mole
of gas 22.4 L You can use this to calculate
the density of a gas in g/Liter at STP. Example
What is the density of CO2 gas at STP? The
molar mass of CO2 12.0111 2(15.9994)
44.0099 g Density mass/volume 44.0099 g/22.4
L 1.96 g/L
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Chemistry SOL Review Molar Relationships
The Mole and Mole Calculations
At Standard Temperature and Pressure (STP) 1 mole
of gas 22.4 L You can use this to calculate
the density of a gas in g/Liter at STP. Example
What is the density of CO2 gas at STP? The
molar mass of CO2 12.0111 2(15.9994)
44.0099 g Density mass/volume 44.0099 g/22.4
L 1.96 g/L You try one What is the density of
Cl2 gas at STP?
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Chemistry SOL Review Molar Relationships
The Mole and Mole Calculations
At Standard Temperature and Pressure (STP) 1 mole
of gas 22.4 L You can use this to calculate
the density of a gas in g/Liter at STP. Example
What is the density of CO2 gas at STP? The
molar mass of CO2 12.0111 2(15.9994)
44.0099 g Density mass/volume 44.0099 g/22.4
L 1.96 g/L You try one What is the density of
Cl2 gas at STP? Answer molar mass 2(35.453)
70.906 g 70.906 g/22.4 L 3.165 g/L
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Chemistry SOL Review Molar Relationships
Stoichiometry
For reaction calculations, the molar ratio is
used. Example How many moles of nitrogen will
react with 9 moles of hydrogen to produce ammonia
according to this equation? 2N2(g) 3 H2(g) ?
2NH3(g) Given 9 moles H2, Find moles
N2
9 mol H2 x 2 mol N2 6 mol N2
3 mol H2
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Chemistry SOL Review Molar Relationships
Stoichiometry
For reaction calculations, the molar ratio is
used. Example 2 How many grams of nitrogen are
needed to react with 2.0 grams of hydrogen using
this equation? 2N2(g) 3 H2(g) ?
3NH3(g) Given 2.0 grams H2, Find grams
N2
2.0 g H2 x 1 mol H2 x 2 mol N2 x 28.014 g N2 18.53 g N2
2.016g H2 3 mol H2 1 mol N2
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Chemistry SOL Review Molar Relationships
Gas Laws

1. General Properties of GasesThere is a lot of
   free space in a gas.Gases can be expanded
   infinitely.Gases fill containers uniformly and
   completely.Gases diffuse and mix rapidly.

Always use degrees Kelvin C 273 K
The Gas Laws The Combined Gas Law
P1V1 P2V2
T1 T2
Boyles Law Inverse relationship
P1V1 P2V2

V1 V2
T1 T2
Charles Law
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Chemistry SOL Review Molar Relationships
Gas Laws
P1V1 P2V2
T1 T2
Some ProblemsA balloon contains 8.0 liters of
gas at 100 K. What is the balloons volume at
200K?
P1V1 P2V2

V1 V2
T1 T2
8 V2
100 200
Answer 16 Liters
A balloon contains 10. Liters at 3 atmospheres
and 275 K. What is the volume of the balloon at
0.50 atmospheres and 200K?
(3.0)(10) (0.50)V2
275 200
Answer 45 Liters
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Chemistry SOL Review Molar Relationships
Gas Laws

• The Ideal Gas Law
• Memorize PV nRT
• P pressure in kPa
• V liters
• N moles
• T temperature in Kelvin
• R universal gas law constant 8.31
• The SOL test uses

kPa x L
Moles x K
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Chemistry SOL Review Molar Relationships
Gas Laws
The Ideal Gas Law Memorize PV nRT
R 8.31 kPa x L
Moles x K
Example 1A 15 liter tank contains 2.0 moles of
nitrogen gas at 27 C. What is the pressure of
nitrogen inside the tank? Answer P?, V15 L,
n2.0, T300K (remember to convert) P(15)2.0(8.31
)(300) so P 332.4 kPa
You try How many moles of Hydrogen gas are in a
20. L tank pressurized to 1000. kPa at 300K?
Answer P1000., V20. L, n? T300K (1000.)(20)
n(8.31)(300) so n 8.0 moles Hydrogen
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Chemistry SOL Review Molar Relationships
Gas Laws
Daltons Law of Partial Pressures Memorize
Ptotal P1 P2 P3
Example A tank containing nitrogen, hydrogen and
ammonia gas has a total pressure of 12
atmospheres. The partial pressure of the
hydrogen is 6 atmospheres, the partial pressure
of the ammonia is 4 atmospheres. What is the
partial pressure of the nitrogen? Answer Ptotal
12 atm, PN2?, PH26, PNH34 12 PN2 6 4
so PN2 2
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Chemistry SOL Review Molar Relationships
Solution Concentrations
Calculating molarity Memorize this equation
Molarity moles/liters or M mol/L Memorize
conversion factor 1000 mL 1 L Some example of
using this equation Example 1 the molarity of
2.0 moles of HCl in a 0.50 L solution of water
is molarity 2.0 mole HCl/0.50 L 4.0 Molar
or 4 M Example 2 The molarity of 0.40 moles of
HCl in a 300. mL L solution of water
is molarity 0.40 moles HCl/0.300. L 1.3 M
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Chemistry SOL Review Molar Relationships
Solution Concentrations
Example 3 The molarity of 72.9 g of HCl in 5.0
liters of aqueous solution is Answer first
calculate the moles of HCl
72.9 g HCl x 1 mol HCl 2.00 mol HCl
36.46 g HCl
Then calculate molarity of solution 2.00 mol
HCl/5.0 L 0.40 M HCl
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Chemistry SOL Review Molar Relationships
Solution Concentrations
You try one What is the molarity of 1.2 grams
LiF in a 50. mL aqeous solution? Answer first
calculate the moles of LiF
1.2 g LiF x 1 mol LiF 0.046 mol LiF
25.94 g LiF
Then calculate molarity of solution (remember
convert mL to Liters) 0.046 mol LiF/0.050 L
0.95 M LiF
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Chemistry SOL Review Molar Relationships
Solution Concentrations

• Diluting concentrated solutions
• Memorize M1V1 M2V2
• M1 and V1 are the beginning molarities and
  volumes
• M2 and V2 are the ending molarities and volumes
• V1 and V2 can be in Liters or mLs, but must be
  the same units for both
• Example
• What is the molarity of a 10. mL sample of 2.0 M
  aqueous HCl diluted to 40. mL
• Answer
• (2.0)(10.) (M2)(40.) so M2 0.5 Molar HCl

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Chemistry SOL Review Molar Relationships
Solution Concentrations

• Diluting concentrated solutions
• Memorize M1V1 M2V2
• M1 and V1 are the beginning molarities and
  volumes
• M2 and V2 are the ending molarities and volumes
• V1 and V2 can be in Liters or mLs, but must be
  the same units for both
• You try one
• How many milliliters of 6.0 Molar HCl are
  required to prepare 240 mL of 2.0 Molar HCl?
• Answer
• (6.0)(V1) (2.0)(240) so V1 80. mL HCl

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Chemistry SOL Review--Molar Relationships
Chemical Equilibrium
Exothermic and Endothermic Reactions
Catalysts lower the Activation energy barrier,
making reactions faster.
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Chemistry SOL Review--Molar Relationships
Chemical Equilibrium
Reversible Reactions Some reactions are
REVERSIBLE, which means that they can go
backwards (from product to reactant) Example
The reaction between nitrogen and hydrogen, where
a ? indicates a reversible reaction N2(g)
3H2(g) ? 2 NH3(g) heat
The forward reaction takes place at the same rate
as the reverse reaction. The equilibrium
position of products and reactants depends on the
conditions of the reaction. If we change the
reaction conditions, the equilibrium changes.
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Chemistry SOL Review--Molar Relationships
Chemical Equilibrium
Reversible Reactions Le Chateliers Principle
If a system at equilibrium is stressed, the
equilibrium will shift in a direction that
relieves that stress. Equilibrium will shift
AWAY from what is added. Here, N2 is added.
N2
More product made
N2(g) 3H2(g) ? 2 NH3(g) heat
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Chemistry SOL Review--Molar Relationships
Chemical Equilibrium
Reversible Reactions Le Chateliers Principle
If a system at equilibrium is stressed, the
equilibrium will shift in a direction that
relieves that stress. Equilibrium will shift
AWAY from what is added. Here, NH3 is added.
NH3
More reactants made
N2(g) 3H2(g) ? 2 NH3(g) heat
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Chemistry SOL Review--Molar Relationships
Chemical Equilibrium
Reversible Reactions Le Chateliers Principle
If a system at equilibrium is stressed, the
equilibrium will shift in a direction that
relieves that stress. Equilibrium will shift
TOWARDS what is removed. Here H2 is removed.
H2
N2(g) 3H2(g) ? 2 NH3(g) heat
More reactants made
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Chemistry SOL Review--Molar Relationships
Chemical Equilibrium
Reversible Reactions Le Chateliers Principle
If a system at equilibrium is stressed, the
equilibrium will shift in a direction that
relieves that stress. Equilibrium will shift
TOWARDS what is removed. Here heat is removed.
heat
N2(g) 3H2(g) ? 2 NH3(g) heat
More product made
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Chemistry SOL Review--Molar Relationships
Chemical Equilibrium

• Methods to Speed up Reactions
• Use a catalyst
• Reduce the particle size
• Increase the heat
• Increase reactant concentration

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Chemistry SOL Review--Molar Relationships
Acid/Base Theory
Acids and Bases Generic formula for acids HX
(HCl, HNO3, H2SO4) Generic formula for bases
MOH where M is any metal (NaOH, KOH, Ca(OH)2
Ammonia, NH3, is also a base. Acid solutions
have a pH less than 7 Basic solutions have a pH
more than 7
Arrhenius acids Taste _______ turn litmus paper
red. Arrhenius bases Taste _______ Feel
__________ Turn litmus paper blue.
SAFETY NOTES Always add acid to water when
diluting If you spill acid or base on yourself,
rinse with lots of water.
sour
bitter
slippery
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Chemistry SOL Review--Molar Relationships
Acid/Base Theory
What is pH? pH indicates the hydrogen ion
molarity H in a solution pH -logH pOH
indicates the hydroxide ion molarity OH- in a
solution. pOH -logOH- Example A 1.0 x 10-3
molar solution of HCl would have a pH of
___ Example A 1.0 x 10-4 molar solution of KOH
would have a pOH of ___ Memorize pH pOH
14. Example A solution with a pH of 8 will have
a pOH of ____.
3
4
6
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Chemistry SOL Review--Molar Relationships
References
http//www.markrosengarten.com/ for New York
Regents exam powerpoint.