Chemistry 112 Name _______________________

Exam II Form A Section _______________________

March 16, 2015 eMail _______________________

IMPORTANT: On the scantron (answer sheet), you MUST clearly fill your name, your student number, section number, and test form (white cover = test form A; yellow cover = test form B). Use a #2 pencil.

There are 25 questions on this exam. Check that you have done all of the problems and filled in the first 25 bubbles on the scantron.Your score will be reported in percent (max 100%).

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• Calculators with text-programmable memory are not allowed. • Relevant data and formulas, including the periodic table, are attached at the end of this

exam. • Your grade will be based only on what is on the scantron form. • The answer key will be posted on the web after the exam (on the Exam Schedule page). • You must turn in your cover sheet with your scantron answer form.

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CHEMISTRY 112 EXAM 2 March 16, 2015

FORM A --------------------------------------------------------------------------------------------------------------------- 1. In the process below, which species are acting as Bronsted acids and bases?

H2O

OH–

A. acid base acid base

B. base acid base acid

C. acid base base acid

D. acid acid base base

E. base acid acid base

--------------------------------------------------------------------------------------------------------------------- 2. Which reaction below should have ΔS > 0 ? A. 2 H2 (g) + O2 (g) → 2 H2O (g)

B. 2 NO2 (g) → N2O4 (g)

C. Ag+ (aq) + Cl− (aq) → AgCl (s)

D. BaF2 (s) + H2O (ℓ) → Ba2+ (aq) + 2 F− (aq)

E. 2 Hg (ℓ) + O2 (g) → 2 HgO (s) --------------------------------------------------------------------------------------------------------------------- 3. A demonstration in class illustrated the acidity and basicity of various oxides. Which one of the following oxides produces an acidic solution when added to water? A. CaO

B. P4O10

C. Al2O3

D. Na2O

E. BaO ---------------------------------------------------------------------------------------------------------------------

H2N

O

NH2 H2N

O

NH3++ H2O OH+

H2N

O

NH2 H2N

O

NH3+

--------------------------------------------------------------------------------------------------------------------- 4. Which of the following solutions would have a pH < 7? i. NH4Cl (aq) ii. CaF2 (aq) iii. Al(NO3)3 (aq) iv. HF (aq) A. iv only

B. i and ii

C. ii and iii

D. i and iv

E. i, iii, and iv --------------------------------------------------------------------------------------------------------------------- 5. Which of the following will have the highest gas-phase entropy at 25°C? A. H2

B. C2H6

C. CH4

D. C3H8

E. C2H2 --------------------------------------------------------------------------------------------------------------------- 6. Solid ammonium nitrate (NH4NO3) is highly soluble in water. When it dissolves, the solution gets cold (i.e., the beaker feels very cold). Based on this information, what are the signs for ΔH and ΔS respectively? A. ΔH is −, ΔS is −

B. ΔH is −, ΔS is +

C. ΔH is +, ΔS is −

D. ΔH is +, ΔS is +

E. ΔH is 0, ΔS is 0 ---------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------- 7. Consider the following titration curve. Which of the following statements is/are TRUE?

i. The acid is a diprotic acid ii. The acid is a triprotic acid iii. Point E represents the third equivalence point iv. Point A represents the first half-equivalence point A. i only B. ii only C. i and iv only D. ii and iii only E. ii, iii, and iv only --------------------------------------------------------------------------------------------------------------------- 8. Which one of the following species cannot be a Lewis base? A. F−

B. H2O

C. OH−

D. NH3

E. NH4+

---------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------- 9. A chemist adds 300 mL of a 0.34 M solution of HCl to 500 mL of a 0.10 M solution of HClO4. What is the pOH of the resulting solution at 25 °C? A. 13.3

B. 11.4

C. 2.06

D. 7.21

E. The pOH cannot be determined from the information provided. --------------------------------------------------------------------------------------------------------------------- 10. Arrange these molecules in order of increasing acid strength.

A. IV < II < I < III

B. II < I < III < IV

C. III < I < IV < II

D. I < III < II < IV

E. II < IV < III < I --------------------------------------------------------------------------------------------------------------------- 11. The equilibrium constant for the reaction shown below is measured at 42.0°C and is found to be 7.59 × 10–6. What is Kw at 42.0°C? (Ka for HA at 42°C: 8.31 × 10–9)

A−(aq) + H2O(ℓ) ⇌ HA(aq) + OH−(aq) A. 1.09 × 10–3

B. 8.31 × 10–9

C. 7.14 × 10–15

D. 1.00 × 10–14

E. 6.31 × 10–14 ---------------------------------------------------------------------------------------------------------------------

O

OH

FH

HH

F

O

OH

ClH

HH

Cl

O

OH

FH

FH

F

O

OH

BrH

HH

Br

I. II. III. IV.

--------------------------------------------------------------------------------------------------------------------- 12. Oh no! A research student working in the lab of Rick T. Cat accidentally mixed up three unlabelled bottles of 0.1 M acid solutions. The three acids are acetic acid, hypochlorous acid, and nitric acid. In order to figure out the identities of the three solutions, Dr. Cat titrates each of the three acid solutions with 0.10 M NaOH. The following data were obtained at 25 oC:

What are the identities of the acid solutions? Ka (CH3COOH) = 1.8 × 10−5 Ka (HClO) = 3.5 × 10−8

Acid 1 Acid 2 Acid 3

A. HClO HNO3 CH3COOH

B. HClO CH3COOH HNO3

C. CH3COOH HClO HNO3

D. CH3COOH HNO3 HClO

E. HNO3 HClO CH3COOH

---------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------- 13. The concentration of ascorbic acid (vitamin C) in a solution is 0.0023 M. What is the

pH of the solution?

Structure of ascorbic acid

For ascorbic acid, Ka1 = 8.0 × 10–5, Ka2 = 1.6 × 10–12 A. 3.4

B. 4.1

C. 6.7

D. 7.2

E. 10.6 --------------------------------------------------------------------------------------------------------------------- 14. Benadryl is an over-the-counter drug that acts as an antihistamine. It is used to treat a number of conditions that include allergies, insomnia, and motion sickness. What is the pH of a 0.0098 M solution of a dose of the liquid form of benadryl at 25 oC? Kb = 1.0 × 10−5 Structure of benadryl:

A. 3.50

B. 4.82

C. 7.00

D. 8.73

E. 10.50 ---------------------------------------------------------------------------------------------------------------------

OO

OHHO

OHHO

--------------------------------------------------------------------------------------------------------------------- 15 Which of the following salts will form an aqueous solution with the highest pH? A. NaIO

B. NaBrO

C. NaClO

D. NaClO2

E. NaClO3 --------------------------------------------------------------------------------------------------------------------- 16. Which of the following statements are true concerning an aqueous solution of phosphoric acid (H3PO4)? The acid dissociation constants of H3PO4 (aq) are: Ka1 = 7.5 × 10−3 , Ka2 = 6.2 × 10−8 , Ka3 = 4.2 × 10−13

i. The strongest conjugate base involved is the PO43– (aq) species.

ii. Both HPO42– (aq) and H2PO4

– (aq) species are amphoteric. iii. HPO4

2– (aq) is a stronger acid than H2PO4– (aq).

A. i only

B. ii only

C. iii only

D. i and ii only

E. ii and iii only --------------------------------------------------------------------------------------------------------------------- 17. Which one of the following mixtures would create a buffer? A. 50 mL of 0.1 M HCl + 50 mL of 0.2 M NaOH

B. 50 mL of 0.1 M HCl + 50 mL of 0.2 M CH3COONa

C. 100 mL of 0.1 M HCl + 50 mL of 0.2 M CH3COONa

D. 100 mL of 0.1 M NaOH + 100 mL of 0.1 M CH3COOH

E. 100 mL of 0.2 M NaOH + 100 mL of 0.1 M CH3COOH ---------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------- 18. Sorbic acid (C5H7COOH) is a monoprotic weak acid with Ka = 1.7 × 10–5. Its salt (potassium sorbate) is added to cheese to inhibit the formation of mold. What is the pH of a 0.0428 M C5H7COOK aqueous solution at 25 °C? A. 12.35

B. 9.58

C. 8.70

D. 5.90

E. 3.46 --------------------------------------------------------------------------------------------------------------------- 19. Kw for water at body temperature (36.9° C) is 2.51 × 10–14. What is the pOH of blood

if the pH is 7.40? A. 5.8

B. 6.2

C. 6.6

D. 7.8

E. 13.6 --------------------------------------------------------------------------------------------------------------------- 20. A scientist titrates 50 mL of a 0.5 M solution of methylamine with 1 M HCl. What is the pH of the solution after 12.5 mL of HCl is added at 25 oC? Kb of methylamine = 4.2 × 10−4 A. 3.4

B. 5.9

C. 7.0

D. 10.6

E. 13.7 ---------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------- 21. Consider the following aqueous solution of aspirin:

Which of the following would cause the equilibrium to shift to the RIGHT at 25 oC? i. Lowering the pH ii. Addition of hydroxide iii. Dissolving more aspirin

iv. Addition of:

A. i only

B. ii only

C. iii only

D. i and iv

E. ii and iii --------------------------------------------------------------------------------------------------------------------- 22. What is the pH of a solution after 0.0400 mole of HNO3 is added to 1.00 L of solution that is 0.100 M in sodium propionate, NaC3H5O2, and 0.300 M in propionic acid, HC3H5O2 assuming the volume does not change upon addition of the HNO3? (Ka for HC3H5O2 = 1.3 × 10−5) A. 4.50

B. 4.08

C. 3.96

D. 4.13

E. 4.62 ---------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------- 23. The famous scientist, Rick T. Cat, found himself at the Mt. Nittany Medical Center with symptoms including hyperventilation, vomiting, dizziness, and a diffuse burning sensation. Upon examination, it was found that his blood concentration of H2CO3 was 1.5 mmol/L, and the concentration of HCO3

− in his blood was 30 mmol/L. What is the pH of his blood? Ka1 of H2CO3 = 4.3 × 10−7 Ka2 of H2CO3 = 5.6 × 10−11 A. 7.33

B. 11.55

C. 6.37

D. 7.67

E. 7.51 --------------------------------------------------------------------------------------------------------------------- 24 After four hours of treatment, Rick T. Cat’s blood pH returned to a stable 7.45. What was the ratio of HCO3

− to H2CO3 in his blood after treatment? Ka1 of H2CO3 = 4.3 × 10−7 Ka2 of H2CO3 = 5.6 × 10−11 A. 12.1

B. 1.08

C. 10.1

D. 0.130

E. 3.22 ---------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------- 25. A scientist titrates 100 mL of a 0.2M solution of lactic acid with 0.1M NaOH. What is the pH of the solution after 200 mL of NaOH is added at 25 oC? Ka (lactic acid) = 1.38 × 10−4 Structure of lactic acid:

A. 5.66 B. 3.86 C. 7.00 D. 11.48 E. 8.34 --------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------

End of Exam

Chem 112 Spring 2015 Exam 2 Answer Key

3/16/15 Form A

1. E 2. D 3. B 4. E 5. D 6. D 7. C 8. E 9. A 10. A 11. E 12. B 13. A 14. E 15. A 16. D 17. B 18. C 19. B 20. D 21. E 22. D 23. D 24. A 25. E