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CHEMISTRY 222
Rogue Community College
HOMEWORK SHEETS – WINTER 2014
to be used with McQuarrie, Rock and Gallogly, General Chemistry (4th edition)
Structures of Molecules & Polyatomic Ions (CH. 8/9) …….…..…………...…….. 1
Molecular Orbitals (CH. 9) ……………..………………..………….…………….. 3
Gas Laws (CH. 13) ………………………………………………………………….. 5
Gas Calculations (CH. 13) ……………………………………………………….….. 7
Intermolecular Forces (CH. 15) ……………………………………………...…….. 9
Condensed Phases (CH. 15) ………………………………………………………… 11
Solutions I (CH. 16) ….…………………………………………………………..... 13
Solutions II (CH. 16) ………………………………………………………………… 15
Kinetics I (CH. 17) ………..………………………………………………………. 17
Kinetics II (CH. 18) ……..….……………………………………………………... 19
Equilibrium I (CH. 19) …………………..………………………………………... 21
Equilibrium II (CH. 19) ……………………..…………………………………….. 23
Acid/Base I (CH. 20) ……………………………...………………………………. 25
Acid/Base II (CH. 20) ………………………………….………………………….. 27
1
Chemistry 222, Rogue Community College
Structures of Molecules & Polyatomic Ions Homework (Ch. 8/9)
Name ___________________________
Molecular
Formula
Number
of v.e.
Lewis Structure
Shape Hybridization
(central atom) Polar or Nonpolar?
H2O
NH3
CH4
SCl6
PCl5
CO2
HCN
SO2
SO3
2
(note that the last column is a different question on the back than on the front)
Polyatomic
Ion
Number
of v.e.
Lewis Structure
Shape Hybridization
(central atom) Numbers of
and bonds
NH4+
H3O+
CO32
NO3
IF4+
N3
ClO3
NH2
ICl4
BrO2
3
Chemistry 222, Rogue Community College
Molecular Orbitals Homework (Ch. 9)
Name ___________________________
1. Two atomic orbitals can interfere with each other to make two molecular orbitals.
(a) What is the name of the molecular orbital formed by constructive interference (i.e.
with most of its electron density in between the two nuclei)?
(b) What is the name of the molecular orbital formed by destructive interference (i.e.
with most of its electron density on the far sides of the two nuclei)?
2. Sketch the molecular orbital energy diagram showing the addition and subtraction of two
1s atomic orbitals to form 1s and *1s molecular orbitals.
3. Use the diagram you drew for question #2 to determine the bond order for each of the
following diatomic molecules (or ions).
Number of Electrons Bond Order
H2 __________ __________
H2+ __________ __________
H2¯ __________ __________
He2 __________ __________
He2+ __________ __________
4
4. Sketch two molecular orbital energy diagrams showing the interference of two 2s and six
2p atomic orbitals to form 2s, *2s, 2p, *2p, 2p, *2p molecular orbitals. Be sure to
label which diagram is used for lithium/beryllium/boron/carbon/nitrogen and which
diagram is used for oxygen/fluorine/neon.
5. Use the diagrams you drew for question #4 to determine the bond order for each of the
following diatomic ions. Use the same diagram for each ion that you would for the
neutral molecule.
Number of Electrons Bond Order
C2+ __________ __________
O2+ __________ __________
C2¯ __________ __________
O2¯ __________ __________
NO+ __________ __________
NO¯ __________ __________
6. Which common diatomic element is paramagnetic? _______________
In which molecular orbitals are the unpaired electrons found? _______________
Note: this is a major success for molecular orbital theory because neither the Lewis
structure nor the valence bond model, can explain this observation.
5
Chemistry 222 – Rogue Community College
Gas Law Homework (Ch. 13)
Name ___________________________
Ideal Gas Law: PV = nRT, where R = 0.08206 Latm/molK
Boyle's Law: P1V1 = P2V2 (n, T constant);
Charles' Law: V1/T1 = V2/T2 (n, P constant)
1. What is the volume of 3.25 moles of ideal gas at 25.0C and 0.759 atm pressure?
2. What pressure is exerted by 0.25 moles of ideal gas at 50.0C and a volume of 1.75 L?
3. How many moles of ideal gas will occupy a volume of 20.0 L at 100.C and 0.275 atm?
6
4. At what temperature (in C) will 1.25 moles of ideal gas occupy a volume of 10.0 L with
a pressure of 0.500 atm?
5. A fixed quantity of gas at 25.00C occupies 3.75 L. If the gas is heated at constant
pressure to 50.00C, what will its new volume be?
6. A fixed quantity of gas at 2.75 atm occupies 3.75 L. If the gas is compressed at constant
temperature to 1.75 L, what will its new pressure be?
7. For the following reaction, (a) calculate the mass of aluminum required in order to
produce 25.0 mL of H2 gas at 23.5C and 0.805 atm, and (b) calculate the volume of
0.150 M HCl required in order to react completely with the mass of aluminum you
calculated in part (a).
2 Al (s) + 6 HCl (aq) 3 H2 (g) + 2 AlCl3 (aq)
7
Chemistry 222 – Rogue Community College
Gas Calculations Homework (Ch. 13)
Name ___________________________
1. What is the density of methane gas at STP?
2. The density of a gas is measured at STP and found to be 1.428 g/L. What is the molecular
weight of the gas? What could be the identity of the gas?
3. If 3.095 g of a pure gaseous substance is found to occupy 3.846 L at 22C and 0.975 atm,
what is the molecular weight of the gas? What is the probable identity of the gas?
4. If a mixture of 10.7% (by volume) CO and 89.3% (by volume) CO2 exerts a total pressure
of 1.75 atm, what are the partial pressures of CO and CO2 in the mixture?
5. If a mixture of 5.25 g CO and 8.43 g CO2 exerts a total pressure of 1.75 atm, what are the
partial pressures of CO and CO2 in the mixture?
8
6. A 98.5 mL sample of H2 gas is collected over water at STP. If the vapor pressure of water
is 0.0325 atm at this temperature, how many moles of H2 were collected?
______ 7. Which of the following gases has the greatest average molecular kinetic
energy at STP?
(A) H2 (B) He (C) N2 (D) all are the same
______ 8. Which of the following gases has the greatest average molecular speed at STP?
(A) H2 (B) He (C) N2 (D) all are the same
______ 9. Which of the following gases has the greatest density (g/L) at STP?
(A) H2 (B) He (C) N2 (D) all are the same
______ 10. Which of the following gases has the greatest concentration (mol/L) at STP?
(A) H2 (B) He (C) N2 (D) all are the same
11. List at least two similarities and two differences between an ideal gas and a real gas.
12. Which gas would you expect to exhibit more obvious non-ideal behavior, H2 or H2O?
Explain your answer.
9
Chemistry 222, Rogue Community College
Intermolecular Forces Homework (Ch. 15)
Name ___________________________
______ 1. Which of the following molecules exhibits hydrogen bonding?
(A) CH4 (B) PH3 (C) H2S (D) H2O
______ 2. Which of the following are intermolecular forces?
(A) dipole-dipole interactions (B) London forces
(C) hydrogen bonding (D) all of the above
______ 3. Which of the following will tend to increase intermolecular forces?
(A) increased molecular weight (B) increased polarity
(C) increased hydrogen bonding (D) all of the above
______ 4. Choose the substance with the highest boiling point:
(A) CH4 (B) NH3 (C) H2O (D) HF
______ 5. Choose the substance with the highest boiling point:
(A) F2 (B) Cl2 (C) Br2 (D) I2
______ 6. Which state of matter has both definite shape and definite volume?
(A) solid (B) liquid (C) gas (D) none
______ 7. Which state of matter has neither definite shape nor definite volume?
(A) solid (B) liquid (C) gas (D) none
______ 8. Which state of matter has definite shape but not definite volume?
(A) solid (B) liquid (C) gas (D) none
10
9. Can nonpolar molecules experience van der Waals forces? Why or why not?
10. Why does ice float on liquid water? Is this the expected behavior of most substances?
Why or why not?
11. Why does water have a relatively high surface tension?
12. Why is glycerol so viscous?
13. Distinguish between the terms surface tension and capillary action.
14. Briefly explain why water's meniscus is curved upward while mercury's meniscus is
curved downward (in glass containers).
11
Chemistry 222, Rogue Community College
Condensed Phases Homework (Ch. 15)
Name ___________________________
1. Distinguish between crystalline solids and amorphous solids. Be accurate, concise and
parallel!
2. Distinguish between metallic solids and ionic solids. Be accurate, concise and parallel!
3. Distinguish between the valence band and the conduction band in a semi-conductor. Be
accurate, concise and parallel!
4. Distinguish between molecular solids and network covalent solids. Be accurate, concise
and parallel!
5. Calculate the amount of heat required in order to transform 10.0 g of liquid water at 25oC
to 10.0 g of water vapor at 175oC. (Look up the necessary constants in Tables 15.3 and
14.6.)
12
6. Describe the terms x-ray diffraction and unit cell.
7. How many atoms are there in a simple cubic unit cell? How many atoms are there in a
bcc unit cell? How many atoms are there in a fcc unit cell? Note: In answering this
question, you must take into account that any corner, face or edge atoms are actually
shared between more than one unit cell!!
8. Why does it take longer to boil an egg in Grants Pass than in Brookings? Include the
concepts of vapor pressure and atmospheric pressure in your answer.
9. On the following phase diagram for an unknown substance, clearly label the melting
point, boiling point, triple point, critical temperature and critical pressure for the
substance.
Pressure
Patm
Temperature
13
Chemistry 222 – Rogue Community College
Colligative Properties I Homework (Ch. 16)
Name ___________________________
1. A solution is prepared by dissolving 10.0 g of (solid) naphthalene (C10H10) in 500.0 g of
(liquid) chloroform (CHCl3). The resulting solution is liquid. Identify the solute and the
solvent.
2. Calculate the molality of the solution from #1.
3. Calculate the mole fractions of C10H10 and CHCl3 in the solution from #1.
4. Calculate the mass percents of C10H10 and CHCl3 in the solution from #1.
5. Calculate the molarity of the solution from #1 if its density is 1.50 g/mL.
14
6. Determine the ideal van’t Hoff i-factor for each of the following aqueous solutions, and
then rank them in order of increasing osmotic pressure.
0.10 M sucrose (C12H22O11) 0.08 M NaCl 0.03 M MgCl2
7. Rank the solutions from #6 in order of increasing vapor pressure.
8. Rank the solutions from #6 in order of increasing boiling point.
9. Rank the solutions from #6 in order of increasing freezing point.
10. 10.0 g of an unknown sugar is dissolved in 100.0 mL of water and the resulting freezing
point is determined to be 0.37C. Calculate the molecular weight of the sugar, given that
Kf for water is 1.86 C/m.
15
Chemistry 222 – Rogue Community College
Colligative Properties II Homework (Ch. 16)
Name ___________________________
1. Clearly state Henry’s Law, and give an example.
2. Clearly state Raoult’s Law, and give an example.
3. Sketch a graph of rate of condensation vs. time for a pure solvent and a solution, and use
it to explain why the vapor pressure of a pure liquid always decreases when a nonvolatile
solute is dissolved in it.
16
5. Sketch a phase diagram (P vs. T) for water and salt water, and use it to explain why the
boiling point of a pure liquid always decreases when a nonvolatile solute is dissolved in
it.
6. If a beaker of pure water and a beaker of diluted sea water are placed under a bell jar,
what will happen to the water level in each of the beakers and why?
7. If pure water and diluted sea water are placed on opposite sides of a semipermeable
membrane in a U-shaped glass tube, what will happen to the water level on each side of
the membrane and why?
8. What is an azeotrope, and why is it important to consider azeotrope formation when
performing a distillation?
17
Chemistry 222 - Rogue Community College
Kinetics I Homework (Ch. 17)
Name ___________________________
1. Identify each of the following statements as TRUE or FALSE. Correct any false
statements.
(a) The rate of a reaction can be expressed as the rate of disappearance of its products
or the rate of appearance of its reactants.
(b) If a compound, C, decomposes to products by a first-order reaction (C pdts),
then rate = −d[C]/dt = k[C].
(c) For the reaction: a A + b B c C + d D, if a plot of [A] vs. time is a straight
line, then the reaction is first-order in [A]. (Assume an excess of [B].)
(d) For the reaction: a A + b B c C + d D, if a plot of ln [A] vs. time is a
straight line, then the reaction is first-order in [A]. (Assume an excess of [B].)
(e) For the reaction: a A + b B c C + d D, if a plot of 1/[A] vs. time is a
straight line, then the reaction is first-order in [A]. (Assume an excess of [B].)
(f) If the reaction: a A + b B c C + d D is zero-order in [A], then a plot of [A]
vs. time will be a straight line with a negative slope. (Assume an excess of [B].)
(g) If the reaction: a A + b B c C + d D is first-order in [A], then a plot of
ln [A] vs. time will be a straight line with a negative slope. (Assume excess [B].)
(h) If the reaction: a A + b B c C + d D is second-order in [A], then a plot of
1/[A] vs. time will be a straight line with a negative slope. (Assume excess [B].)
18
2. Given the following data, determine the rate law for the following reaction:
2 N2O5 (g) 4 NO2 (g) + O2 (g)
[N2O5]o (M) Initial Rate (M/s)
0.10 1.8 x 10-5
0.20 3.6 x 10-5
0.30 5.4 x 10-5
3. Calculate the rate constant, k, and half-life, t1/2, for the reaction in #2. Be sure to include
the correct number of significant figures and the appropriate units in your answer.
4. Given the following data, determine the rate law for the following reaction:
2 NO (g) + F2 (g) 2 NOF (g)
[NO]o (M) [F2]o (M) Initial Rate (M/s)
0.10 0.10 2.1 x 10-3
0.10 0.20 4.2 x 10-3
0.20 0.10 8.4 x 10-3
5. Calculate the rate constant, k, for the reaction in #4. Be sure to include the correct number
of significant figures and the appropriate units in your answer.
19
Chemistry 222 - Rogue Community College
Kinetics II Homework (Ch. 18)
Name ___________________________
1. If the following first-order reaction has a rate constant of 1.4 x 107 s1, calculate the time
required for [A]o = 0.175 M to reach [A] = 0.100 M. A + B C
2. The reaction 2 A + B C + D follows the rate law: rate = k[B]2. The second-order
rate constant is equal to 2.9 x 104 M1 s1. How long will it take for an original
concentration, [B]o = 0.0500 M to reach 0.0400 M?
3. Identify all of the reactants, products, catalysts and intermediates in the following
sequence of elementary steps for the oxidation of V3+ to Fe3+.
Fe3+(aq) + Mn2+(aq) Fe2+(aq) + Mn3+(aq)
Fe3+(aq) + Mn3+(aq) Fe2+(aq) + Mn4+(aq)
V3+(aq) + Mn4+(aq) V5+(aq) + Mn2+(aq)
20
4. HCl reacts with propene, CH3CH=CH2 in the gas phase according to the overall reaction:
HCl + CH3CH=CH2 CH3CHClCH3. The measure rate law is d[CH3CH=CH2]/dt =
k[HCl]3[CH3CH=CH2]. Which, if any, of the following mechanisms is/are consistent
with the observed rate law?
(a) HCl + HCl H + HCl2 fast
H + CH3CH=CH2 CH3CHCH3 slow
HCl2 + CH3CHCH3 CH3CHClCH3 + HCl fast
(b) HCl + HCl H2Cl2 fast
HCl + CH3CH=CH2 CH3CHClCH3* fast
CH3CHClCH3* + H2Cl2 CH3CHClCH3 + 2 HCl slow
(c) HCl + CH3CH=CH2 H + CH3CHClCH2 fast
H + HCl H2Cl fast
H2Cl + CH3CHClCH2 CH3CHClCH3 + HCl slow
5. The following reaction mechanism has been proposed for a chemical reaction:
A2 A + A fast
A + B AB slow
AB + CD AC + BD fast
(a) Write a balanced equation for the overall reaction
(b) Write a rate law that corresponds to the mechanism above. Express the rate in
terms of concentrations of reactants only.
6. If the rate constant for a chemical reaction is 5.5 x 102 s-1 at 250 K, calculate the value of
the rate constant at 350 K. The activation energy for the reaction is 475 J/mol.
7. If the rate constant for a chemical reaction is 8.9 x 105 M-1 s-1 at 25.0C and 9.9 x 105
M-1 s-1 at 50.0C, calculate the value of the rate constant at 100.0C. What is the
activation energy for this reaction?
21
Chemistry 222 - Rogue Community College
Equilibrium I Homework (Ch. 19)
Name ___________________________
1. Write an equilibrium constant expression (K) for each of the following reactions. Use
partial pressures for all gases and concentrations for all solutes.
(a) CaCO3 (s) Ca2+ (aq) + CO32 (aq)
(b) CaCO3 (s) CaO (s) + CO2 (g)
(c) 2 KClO3 (s) 2 KCl (s) + 3 O2 (g)
(d) 2 HgO (s) 2 Hg (liq) + O2 (g)
(e) 2 Hg (liq) + O2 (g) 2 HgO (s)
(f) HgO (s) Hg (liq) + 2
1 O2 (g)
22
2. Consider the following equilibrium:
N2 (g) + 3 H2 (g) 2 NH3 (g)
Once equilibrium is achieved at room temperature, the concentrations of the gases are measured
and found to be (in moles per liter): [N2] = 5.0 x 10-4, [H2] = 1.0 x 10-3, and [NH3] = 2.0 x 10-3.
Calculate the value of the equilibrium constant (Kc) at room temperature. Watch significant
figures!
3. For the reaction in #2, calculate the numerical value of the equilibrium constant (Kp) at
room temperature given the following equilibrium partial pressures. Watch significant figures!
P(N2) = 0.0183 atm P(H2) = 0.101 atm P(NH3) = 0.500 atm
4. Are your answers to #2 and #3 consistent with the relationship Kp = Kc(RT)? Explain.
5. What is Kp at room temperature for 2 NH3 (g) N2 (g) + 3 H2 (g) ?
23
Chemistry 222 - Rogue Community College
Equilibrium II Homework (Ch. 19)
Name ___________________________
The equilibrium constant (Kp) for the reaction H2 (g) + I2 (g) 2 HI (g)
is 3.1 x 103 at 430C.
1. Starting with 0.100 atm HI (g) only, what will be the equilibrium partial pressures of H2,
I2 and HI?
2. Starting with 0.0100 atm H2 and 0.0100 atm I2 only, what will be the equilibrium partial
pressures of H2, I2 and HI?
3. Starting with 0.0100 atm H2, 0.0500 atm I2 and 0.100 atm HI,
(a) calculate the reaction quotient, Q
(b) which way will the reaction proceed, to the left or to the right?
(c) calculate the equilibrium partial pressures of H2, I2 and HI.
24
4. For the following reaction, determine the effect of each of the following changes on both
the rate of reaction and the equilibrium position. Include a brief explanation of your reasoning.
N2 (g) + 3 H2 (g) 2 NH3 (g) + 22.1 kcal/mol
increase in temperature:
RATE OF REACTION increase decrease no change
EQUILIBRIUM SHIFT right left no shift
increase in pressure/decrease in volume:
RATE OF REACTION increase decrease no change
EQUILIBRIUM SHIFT right left no shift
increase in [H2]:
RATE OF REACTION increase decrease no change
EQUILIBRIUM SHIFT right left no shift
increase in [NH3]:
RATE OF REACTION increase decrease no change
EQUILIBRIUM SHIFT right left no shift
addition of a catalyst:
RATE OF REACTION increase decrease no change
EQUILIBRIUM SHIFT right left no shift
25
Chemistry 222 - Rogue Community College
Acids & Bases I Homework (Ch. 20)
Name ___________________________
1. Write the formula for the conjugate base of each of the following acids:
HC2H3O2 __________ H2O __________
HCO3− __________ H3PO4 __________
NH4+ __________ H3O+ __________
2. Write the formula for the conjugate acid of each of the following bases:
NH3 __________ H2O __________
HCO3− __________ F− __________
PO43− __________ OH− __________
3. Calculate the pH, pOH and [OH] of a solution with [H3O+] = 1.7 x 104 M.
(Watch significant figures! In pH and pOH, only the digits to the right of the decimal
point are significant!)
4. Calculate the [H3O+], [OH] and pOH of a solution with pH = 10.53. Watch sig. figures!
26
5. Distinguish between the terms strong acid and weak acid, and give an example of each.
6. Distinguish between the terms strong base and weak base, and give an example of each.
7. If the Ka for acetic acid (CH3COOH) is 1.8 x 105, what is the Kb for acetate ion
(CH3COO)? Show your work.
8. Calculate the pH of 0.100 M HCl.
9. Calculate the pH of 0.100 M acetic acid (CH3COOH) with Ka = 1.8 x 105.
10. Calculate the pH of 0.0500 M ammonia (NH3) with Kb = 1.8 x 105.
27
Chemistry 222 - Rogue Community College
Acids & Bases II Homework (Ch. 20)
Name ___________________________
1. Calculate the pH and equilibrium concentrations ([H2CO3], [HCO3] and [CO3
2]) for a
0.0750 M solution of carbonic acid. Ionization constants can be found in Table 15.6.
2. Calculate the pH and equilibrium concentrations ([H2SO4], [HSO4] and [SO4
2]) for a
0.0150 M solution of sulfuric acid.
3. Calculate the pH and equilibrium concentrations ([H3PO4], [H2PO4], [HPO4
2] and
[PO43]) for a 0.0325 M solution of phosphoric acid.
28
4. Without looking them up, and based on chemical reasoning, choose the stronger acid
from each of the following pairs. (Circle your answers.)
HClO3 or HClO4 HNO3 or H3PO4 H2PO4 or HPO4
2
5. Write the formula for each of the following compounds, and predict whether it will
produce an acidic, basic or neutral solution. (Circle your answers.)
sodium chloride: acidic basic neutral
ammonium chloride: acidic basic neutral
magnesium oxide: acidic basic neutral
carbon dioxide: acidic basic neutral
sulfur dioxide: acidic basic neutral
diphosphorus pentoxide: acidic basic neutral
potassium oxide: acidic basic neutral
aluminum chloride: acidic basic neutral
potassium cyanide: acidic basic neutral
ammonium sulfate: acidic basic neutral
ammonium acetate: acidic basic neutral
ammonium carbonate: acidic basic neutral
6. Distinguish between the terms Lewis acid and Lewis base.
7. Identify the Lewis acid and the Lewis base in each of the following reactions:
BF3 (g) + NH3 (g) BF3NH3 (s)
H2O (l) + CO2 (g) H2CO3 (aq)
Al3+ (aq) + 6 H2O (l) Al(H2O)63+