Chemistry 20 Final Exam Review
Problems
1. Ionic and molecular (including acids) compounds: naming, formulas, and molar mass.
For each of the following, indicate the name/formula and molar mass:
a. chromium(III) chlorate
b. sulfurous acid
c. copper(I) hydrogen
phosphate
d. phosphorus trichloride
e. lead(II) thiosulfate
f.
g.
h.
i.
j.
NaHCO3
(NH4)3PO4
H2SO4
N 2O
CoCl2
2. Lewis diagrams and bonding
a. Draw the Lewis diagram for phosphorous trichloride.
b. If an atom (X) has 5 valence electrons, what type of bond (ionic,
single/double/triple covalent bond) will be present in X2?
c. If molecule A has 7 valence electrons, molecule B has 1, molecule C has 4 and
molecule D has 6, what will the following compounds look like (bond type)?
i. C2B4D
iii. D2C
ii. CA3B
iv. C2B2
3. VSEPR theory: molecular shape and valence electrons
a. Give an example of a molecule that is
i. Linear
ii. Bent
iii. Trigonal pyramidal
iv. Trigonal planar
v. Tetrahedral
4. Polarity of compounds and electronegativity
a. Arrange these bonds in order of increasing polarity: carbon with oxygen,
hydrogen, chlorine, iodine. Classify them as non-polar covalent, polar covalent,
or ionic.
b. Indicate if each molecule is polar or non-polar:
i. Methane
iii. Water
ii. Ammonia
iv. Hydrochloric acid
5. Melting/Boiling points: indicate which of the following will boil at the highest
temperature based on bonding theory (London forces, dipole-dipole, hydrogen bonds):
a. Ammonia
c. Hydrogen
b. Carbon dioxide
d. Methane
6. Pressure unit conversions
a. If the pressure changes from 55kPa to 98 kPa, what is the change in pressure in
bars? In mmHg? In atm?
7. Gas Law calculations: Charles, Boyle, Gay-Lussac, Combined gas law, Ideal gas law,
Partial pressures, Molar volume
a. If a sample of neon occupies 35.8L at 250K and 1.00 atm of pressure, what
amount of neon is in the beaker?
b. If there are 250 molecules of hydrogen in a certain volume, how many molecules
of fluorine will be present at the same temperature, pressure and volume?
c. What factors affect molar volume?
d. The volume of a fixed mass of gas decreases from 45 ml to 4.5 ml. How will the
temperature be affected?
e. If pressure remains constant, what volume will a gas occupy at 26°C if it occupied
32 L at 0.0°C?
f. A flexible container holds 250 mL of nitrogen gas at a pressure of 1.25 atm. If
the pressure is increased to 5.6 bar at a constant temperature of 37 oC, what is
the new volume of the container? What mass of gas is inside the container?
g. A weather balloon has a volume of 15 L under STP conditions. The balloon is
released into the atmosphere and after 15 minutes, it has a pressure of 82 kPa
and a temperature of –39oC. What is the new volume of the balloon?
h. Determine the pressure in a 50 L compressed air tank if 30 mol of air is present
in the container at 30oC.
i. What should happen to the molar volume of a gas if the pressure exerted on it is
doubled when its absolute temperature is halved?
8. KMT (Gas behavior)
a. How does an ideal gas behave?
b. How does the behavior of a gas change at low temperatures or high pressure?
9. Solution basics
a. How is solubility affected by temperature and pressure (in solids, liquids and
gasses)?
b. Dissociation reactions: write a dissociation reaction for the following. (Note that
some compounds may be insoluble!)
i. Potassium chloride
ii. Silver fluoride
iii. Aluminum oxalate
iv. Sodium hydroxide
c. Solubility calculations (saturated, unsaturated solutions):
i. If the solubility of potassium chloride is 34g/100mL at 20°C, will the
solution be saturated or unsaturated if 16 g are dissolved in 50 mL of
water?
10. Concentration: mass/mass, mass/volume, volume/volume, ppm, ppb, molar
a. If 45 mg of calcium chloride was dissolved in 3.0 L of water, what is the
concentration in ppm?
b. If the label reads 12% m/V, what mass of NaCl is dissolved in 250 mL of solution?
c. If 12 g of solid NaNO3 is dissolved to make 200 mL of solution, what is the molar
concentration?
d. If 325 mL of 0.450 mol/L sodium carbonate is made, what mass of sodium
carbonate was dissolved to make the solution?
e. What mass of solid reactant must be dissolved in 450 mL of pure water to make
a 0.17 mol/L ammonium carbonate solution? What is the molar concentration
of each ion in this solution?
f. 250 g of copper(II) sulfate is dissolved in 14750 mL of water. What is the molar
concentration of this solution? What is the molar concentration of each ion in
this solution?
11. Dilution (C1V1 = CfVf)
a. Water is added to 3.0 mol/L sulfuric acid to prepare 1.00 L of 0.250 mol/L sulfuric
acid. What volume of concentrated sulfuric acid was required to prepare this
solution?
b. Water is added to 145 mL of 2.40 mol/L ammonia solution until the solution
reaches a volume of 1.00 L. What is the new molar concentration of this
ammonia solution?
c. Describe completely how you would prepare 100 mL of 1.50 mol/L sulfuric acid
by dilution of a 17.8 mol/L stock solution.
d. Describe the steps to prepare 0.100 mol/L sodium phosphate from a solid.
12. pH/pOH calculations, [H3O+], [OH-]
a. If 3.7 g of sodium hydroxide is dissolved in enough water to make 3250 mL of
solution, what is the pOH?
b. Calculate the pH of a solution that has 150 g of hydrogen chloride gas completely
dissolved in 2350 mL of water.
Solution
Key measurement
1.
pH = 12.95
2.
[H3O+] = 8.86 x 10-1 mol/L
3.
[OH-] = 2.97 x 10-12 mol/L
4.
pOH = 1.18
c. Put these solutions in order based on ascending pOH.
13. Equations
a. Writing balanced equations:
i. the combustion of cyclohexane (C6H12(l))
ii. the formation of calcium nitrite
iii. the decomposition of zinc permanganate
iv. the reaction between potassium sulfate and barium nitrate
v. the reaction between copper and chromium(III) chlorate
b. Ionic and net ionic equations: Write ionic equations for each and determine
which ions are the spectator ions
i. the reaction between potassium sulfate and barium nitrate
ii. the reaction between copper and chromium(III) chlorate
14. Stoichiometry (mass, solution, gas)
a. In the reaction between copper(II)nitrate and sodium hydroxide solution, what
mass of precipitate will form if 23 g of copper is used?
b. When 13.0g of potassium chlorate decomposes, what volume of oxygen gas is
produced at 25°C and 766mmHg pressure?
c. In the balanced reaction between potassium permanganate and iron(III)oxalate,
0.24L of potassium permanganate is required to react completely with 2.7g of
iron(III) oxalate. What is the molar concentration of the iron(III) oxalate?
15. Limiting Reactant: determining which reactant is present in the lower amount based on
the mole ratio in the balanced reaction.
a. In a balanced reaction between sodium hydroxide and hydrochloric acid, which
is the limiting reagent if 3.00g of each reactant are used?
b. A solution of aluminum chloride is mixed with a solution of ammonium
hydroxide to form a precipitate. If 200 mL of 0.300 mol/L aluminum chloride is
mixed with 150 mL of 0.200 mol/L ammonium hydroxide, then what is the
concentration of the Al3+ ions remaining un-reacted in solution after the reaction
is complete?
16. Percent Yield
a. A student mixes 5.00 g of zinc with 750 mL of 0.199 mol/L silver nitrate. After
collecting the silver produced by the reaction, the mass of silver is measured to
be 13.30 g. What is the percent yield for this experiment?
17. Acid Base Titrations
a. How to choose an indicator
b. Calculations: 2.56 g of HI(aq) is dissolved in 500 mL of water and 8 g of NaOH is
dissolved in 2000 mL of water. If a 20.0mL aliquot of HI(aq) is titrated with
NaOH(aq), determine the volume of titrant required.