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Chem. 1B Final Practice Test 2

Name__________________________________________ Print Neatly. You will lose 1 point if I cannot read your name or perm number.

Student Number _________________________________

If you are sitting next to someone with the same version of the test, you will be moved and lose 5

points.

All work must be shown on the exam for partial credit. Points will be taken off for incorrect or

no units. Calculators are allowed. Cell phones may not be used for calculators. On fundamental

and challenge problems you must show your work in order to receive credit for the problem. If

your cell phone goes off during the exam you will have your exam removed from you.

Fundamentals (of 72 possible)

Problem 1 (of 13 possible)

Problem 2 (of 17 possible)

Problem 3 (of 18 possible)

Problem 4 (of 20 possible)

Multiple Choice (of 60 possible)

Extra Credit (of 5 possible)

Final Total (of 200 possible)

First letter

of last name

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Fundamental Questions Each of these fundamental chemistry questions is worth 6 points. You must show work to get

credit. Little to no partial credit will be rewarded. Make sure your answer includes the proper

units.

1) 6 pts The equilibrium constant K for the following reaction at 900°C is 0.0028.

What is KP at this temperature?

CS2(g) + 4H2(g) ⇌ CH4(g) + 2H2S(g)

2) 6 pts When 1 mol of a fuel burns at constant pressure it produces 3452 kJ of heat

and does 11 kJ of work. What are the values of ΔE and ΔH for the

combustion of the fuel? Report your answer in 𝑘𝐽

𝑚𝑜𝑙

3)

6 pts

If ΔH is -12.4 𝑘𝐽

𝑚𝑜𝑙 and ΔS is 0.91 𝐽

𝑚𝑜𝑙∙𝐾 what is ΔG at 75°C and is the reaction

spontaneous.

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4) 6 pts What is the molar solubility of CaF2 in 0.010 M LiF?

5) 6 pts

ΔG°rxn for 2SO2(g) + O2(g) 2SO3(g) is -141.74 𝑘𝐽𝑚𝑜𝑙

at 25.00°C. What is

ΔGrxn when the partial pressure of each gas is 100. atm? What is the

spontaneous direction of the reaction under these conditions?

6) 6 pts What is K for the following reaction at 25°C?

Sn4+(aq) + 2Ag(s) Sn2+(aq) + 2Ag+(aq) E°=0.65 V

Are there more reactants or products at equilibrium?

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7) 6 pts The preparations of two aqueous solutions are described in the table below.

For each solution, write the chemical formulas of the major species present

at equilibrium. You can leave out water itself.

Write the chemical formulas of the species that will act as acids in the 'acids'

row, the formulas of the species that will act as bases in the 'bases' row, and

the formulas of the species that will act as neither acids nor bases in the

'other' row.

You will find it useful to keep in mind that NH3 is a weak base.

0.5 mol of HNO3 is added to 1.0 L of a 0.5

NH3 solution.

acids:

bases:

other:

0.1 mol of NaOH is added to 1.0 L of a

solution that is 0.3 M in both NH3 and

NH4Br.

acids:

bases:

other:

8) 6 pts A solution has a pH of 4.90, what is the pOH, [H+], and [OH-]?

9) 6 pts What is Ecell for the following reaction at 25°C?

I2(s)+ Fe(s)Fe2+(aq, 0.20 M) + 2I-(aq, 0.30 M)

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10) 6 pts A piece of iron of mass 20.0 g at 100.°C is placed in a vessel of negligible

heat capacity but containing 50.7 g of water at 22.0°C. Calculate the final

temperature of the water. Assume that there is no energy lost to the

surroundings.

11)

6 pts

Consider the following exothermic reaction at 25°C and 1 atm.

2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)

Circle the correct answer for each of the following quantities: w, ΔH, ΔE, ΔS, and ΔG.

w<0 w>0 w=0

ΔH<0 ΔH>0 ΔH=0

ΔE<0 ΔE>0 ΔE=0

ΔS<0 ΔS>0 ΔS=0

ΔG<0 ΔG>0 ΔG=0

12) 6 pts Identify if the following reactions are redox reactions or not. If they are

redox reactions, specify what is oxidized and what is reduced.

Cu(OH)2(s) + 2HNO3(aq) Cu(NO3)2(aq) + 2H2O(l)

Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g)

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Challenge Questions

Each of the following short answer questions are worth the noted points. Partial credit will be

given. Make sure to show work, report answers to the correct number of significant figures and

use the proper units.

1) 13 pts A metal forms the salt MCl3. Electrolysis of the molten salt with a current

of 0.700 A for 6.63 h produced 3.00 g of the metal. What is the molar mass

of the metal?

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2) 17 pts Consider the process

A(l, 75°C) A(g, 155°C)

which is carried out at constant pressure. The total ΔS for this process is

known to be 75.0 𝐽

𝐾∙𝑚𝑜𝑙. For A(l) and A(g), CP values are 75.0 𝐽

𝐾∙𝑚𝑜𝑙, and

29.0 𝐽

𝐾∙𝑚𝑜𝑙, respectively, and are not dependent on temperature. Calculate

ΔHvap for A(l) at 125°C (its boiling point).

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3) Calculate the number of moles of HCl(g) that must be added to 1.0 L of

1.0 M NaC2H3O2 to produce a solution buffered at each pH.

3a) 6 pts pH = pKa

3b) 6 pts pH = 4.20

3c) 6 pts pH = 5.00

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4a) 10 pts A technician carries out the reaction 2SO2(g) + O2(g) 2SO3(g) at 25˚C

and 1.00 atm in a constant-pressure cylinder fitted with a piston. Initially,

0.0300 mol SO2 and 0.0300 mol O2 are present in the cylinder. The

technician then adds a catalyst to initiate the reaction. How much work

takes place, and is it done by the system or on the system. Assume that the

reaction goes to completion and the temperature of the system is constant.

4b) 6 pts What is the change in enthalpy for the reaction in J?

4c) 4 pts What is the change in internal energy for the reaction in J?

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Multiple Choice Questions Each of the following multiple choice questions are worth 5 points. Your

answers need to be filled in on the Scantron provided. Note: Your

Scantrons will not be returned to you, therefore, for your records, you may

want to mark your answers on this sheet. On the Scantron you need to fill

in your perm number, test version, and name. Failure to do any of these

things will result in the loss of 1 point. Your perm number is placed and

bubbled in under the “ID number”. Do not skip boxes or put in a hyphen.

In addition, leave bubbles blank under any unused boxes. The version

number (A) is bubbled in under the “test form.”

1.The pH of a 0.10 M solution of a weak base is 9.82. What is the Kb for this base?

A) 6.6 10-4

B) 4.3 10-8

C) 2.0 10-5

D) 2.1 10-4

E) None of the above

2. For the vaporization of a liquid at a given pressure,

A) G is negative at all temperatures.

B) G is negative at low temperatures but positive at high temperatures (and zero at

some temperature).

C) G is positive at all temperatures.

D) G is positive at low temperatures but negative at high temperatures (and zero at

some temperature).

3. Predict which of the following reactions has a negative entropy change.

I. CH4(g) + 2O2(g) CO2(g) + 2H2O(l)

II. NH3(g) + HCl(g) NH4Cl(s)

III. 2KClO4(s) 2KClO3(s) + O2(g)

A) II

B) I and II

C) I

D) III

E) II and III

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4.Arrange the following 0.10 M solutions from lowest to highest pH: NaF, NaC2H3O2,

C5H5NHCl, KOH, HCN. (Ka for HCN is 6.2 10–10; Ka for HF is 7.2 10–4; Ka for HC2H3O2

is 1.8 10–5; and Kb for C5H5N is 1.7 10–9)

A) HCN, C5H5NHCl, NaF, NaC2H3O2, KOH

B) C5H5NHCl, HCN, NaF, NaC2H3O2, KOH

C) NaF, NaC2H3O2, HCN, C5H5NHCl, KOH

D) KOH, NaC2H3O2, NaF, HCN, C5H5NHCl

E) None of the above

5. For a reaction in a voltaic cell, both H° and S° are positive. Which of the following

statements is true?

A) G° > 0 for all temperatures.

B) E°cell will increase with an increase in temperature.

C) E°cell will decrease with an increase in temperature.

D) E°cell will not change when the temperature increases.

E) None of the above statements is true.

Use the following to answer questions 4-5:

Consider the equation 2A(g) 2B(g) + C(g). At a particular temperature, K = 1.6 104.

6. Raising the pressure by lowering the volume of the container will

A) cannot be determined

B) none of the these

C) cause [B] to increase.

D) have no effect.

E) cause [A] to increase.

7. If you mixed 5.0 mol B, 0.10 mol C, and 0.0010 mol A in a 1-L container, in which direction

would the reaction initially proceed?

A) The above mixture is the equilibrium mixture.

B) To the left.

C) We cannot tell from the information given.

D) To the right.

8. A concentration cell is constructed using two Ni electrodes with Ni2+ concentrations of 1.26 M

(cathode) and 4.95 10–4 M (anode) in the two half-cells. The reduction potential of Ni2+ is –

0.23 V. Calculate the potential of the cell at 25°C.

A) +0.101 V

B) +0.331 V

C) –0.201 V

D) –0.0287 V

E) –0.232 V

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9. At 25°C, the following heats of reaction are known:

2C2H2 + 5O2 4CO2 + 2H2O H = –2600.0 kJ

C + O2 CO2 H = –394 kJ

2H2 + O2 2H2O H = –572 kJ

At the same temperature, calculate ΔH for the following reaction:

2C + H2 C2H2 H = ?

10. Of the following five ions or molecules, which is the strongest reducing agent?

A) Cl2

B) Fe2+

C) Cr2+

D) F-

E) H2

11. Ammonium metavanadate reacts with sulfur dioxide in acidic solution as follows (hydrogen

ions and H2O omitted):

xVO3– + ySO2 xVO2+ + ySO4

2–

The ratio x : y is

A) 2 : 1

B) 1 : 1

C) 1 : 3

D) 1 : 2

E) None of the Above

12. The following reaction has a G° value of 42.6 kJ/mol at 25°C.

HB(aq) + H2O(l) H3O+(aq) + B–(aq)

Calculate Ka for the acid HB.

A) 3.41 10–8

B) 14.0

C) 42,600

D) –17.2

E) 1.63

A) 2422 kJ

B) 226 kJ

C) -2422kJ

D) -226 kJ

E) none of these