CHEMISTRY 222 Rogue Community College HOMEWORK SHEETS ...go.roguecc.edu/sites/go.roguecc.edu/files/users/DSwain/Chem222/C… · HOMEWORK SHEETS – WINTER 2014 to be used with McQuarrie,

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


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


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?


______ 9. Which of the following gases has the greatest density (g/L) at STP?


______ 10. Which of the following gases has the greatest concentration (mol/L) at STP?


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


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?


______ 8. Which state of matter has definite shape but not definite volume?


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


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


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


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


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


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


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:



increase in [H2]:



increase in [NH3]:



addition of a catalyst:



25


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


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+

Documents

CHEMISTRY 222 Rogue Community College HOMEWORK SHEETS ...go.roguecc.edu/sites/go.roguecc.edu/files/users/DSwain/Chem222/C… · HOMEWORK SHEETS – WINTER 2014 to be used with McQuarrie,