South Pasadena AP Chemistry



Name _______________________________

Period ___ Date ___/___/___

Acid-Base Reactions PRACTICE TEST

1. HCN is a weak acid (Ka = 6.2 x 10¯10). NH3 is a weak base (Kb = 1.8 x 10¯5). A 1.0 M solution of NH4CN would be

a) strongly acidic c) neutral

b) weakly acidic d) weakly basic

2. If you mix equal molar quantities of NH3

(Kb = 1.8 x 10−5) and HF (Ka = 7.2 x 10−4), the resulting solution will be

a) acidic because Ka of NH4+ > Kb for F−

b) acidic because Ka of NH4+ > Ka for HF

c) basic because Kb of NH4+ > Kb for F−

d) basic because Ka of NH4+ > Kb for F−

e) neutral

3. How many moles of HCOONa must be added to 1.0 L of 0.10 M HCOOH to prepare a buffer solution with a pH of 3.4? (HCOOH Ka = 2 x 10¯4)

a) 0.01 c) 0.1

b) 0.05 d) 0.2

4. The acid-base indicator methyl red has a Ka of 1 x 10¯4. Its acidic form is red while its alkaline form is yellow. If methyl red is added to a colorless solution with a pH = 7, the color will be

a) pink c) orange

b) red d) yellow

5. Which would make the best aqueous buffer solution?

a) 0.30 M NH3 / 0.30 M NH4Cl

b) 0.010 M NH3 / 0.30 M NH4Cl

c) 0.10 M NH3 / 0.20 M HCl

d) 0.30 M KOH / 0.30 M HCl

6. If you mix equal molar quantities of the following substances, how many will produce an acidic solution?

Set 1: NaOH + HCl

Set 2: NaOH + HNO3

Set 3: NH3 + HCl

Set 4: NaOH + HC2H3O2

a) four d) one

b) three e) zero (none)

c) two

7. A 25.0 mL sample of a 0.20 M solution of a weak monoprotic acid is titrated with a 0.10 M KOH solution. What volume of base is needed to reach the equivalence point?

a) 20.0 mL c) 35.0 mL

b) 25.0 mL d) 50.0 mL

8. We add 200. mL of 0.10 M KOH to 50.0 mL of 0.40 M HF. What is the pH of the resulting solution? Kb for F− = 1.4 x 10−11

a) 5.97 d) 8.37

b) 6.32 e) 9.32

c) 8.02

9. What are the products of the following acid-base reaction?

NaOH(aq) + HF(aq) (

a) NaF(aq) and H2O(l)

b) NaH(aq) and HOF(aq)

c) H2O only.

d) H2O(l), F2(aq), and Na(s)

e) NaF(aq) and OH−(aq)

10. The titration curve below represents the titration of a weak acid with a strong base.

[pic]

What is the Ka of the weak acid?

a) 1.6 x 10-4 c) 1.0 x 10-7

b) 2.0 x 10-6 d) 1.0 x 10-9

11. The salt produced by the reaction of an equal number of moles of KOH and HNO3 will react with water to give a solution which is

a) acidic. d) non-ionic.

b) basic. e) impossible to

c) neutral. determine.

12. If you mix 100. mL of 0.11 M HCl with 50.0 mL of 0.22 M NH3, what is the pH of the resulting solution?

The Ka of NH4+ = 5.6 x 10−10

a) 4.63 d) 8.37

b) 5.19 e) 9.37

c) 6.02

Use the sample data below to answer the next 4 questions.

PART I STANDARDIZATION OF THE

BASE with Solid Acid

|Trial #1 |Acid |Base (NaOH) |RATIO: |

| | | |vol base / mass acid|

|Final Value |2.56 grams |22.50 mL | |

|Initial Value |3.28 grams |0.00 mL | |

|Mass or Volume |? |? | |

|Used | | | |

|Trial #2 |Acid |Base (NaOH) |RATIO: |

| | | |vol base / mass acid|

|Final Value |1.85 grams |45.50 mL | |

|Initial Value |2.56 grams |22.50 mL | |

|Mass or Volume |? |? | |

|Used | | | |

13. What is the percentage difference between the two calculated ratios for trials 1 and 2?

a) 0.45 % c) 2.4 %

b) 1.2 % d) 3.5 %

14. Based on the answer to question #21, should

this student run a third trial for Part I?

a) Yes

b) No

c) More information is needed

15. If the solid acid used above was potassium hydrogen tartrate (KHC4H4O6 M.W. = 188.15), how many moles of OH− in trial #1 were needed to completely neutralize the acid?

a) 0.0174 moles c) 0.00377 moles

b) 0.00766 moles d) 0.00383 moles

16. Based on the data from trial #2, what is

the calculated concentration of the NaOH?

a) 0.16 M c) 0.19 M

b) 0.18 M d) 0.20 M

* * * * * * * * * * * * * * * * * * * * * * * * * *

17. A 10.0 mL sample of 0.15 M HCl is titrated with an NaOH solution. When a 10.0 mL sample of 0.15 M HF (Ka = 7.2 x 10−4) is used, the volume of base needed is

a) the same d) slightly more

b) much more e) slightly less

c) much less

18. A buffer solution is prepared with a pH of 5.50. The solution is diluted by adding an equal volume of distilled H2O. The pH of

the solution will

a) increase slightly d) decrease greatly

b) decrease slightly e) remain the same

c) increase greatly

19. Which graph shows a strong base being titrated with a strong acid?

[pic]

a) Graph (A) d) Graph (D)

b) Graph (B) e) none of these

c) Graph (C)

20. If you titrate HC2H3O2 with NaOH, what species are present at the endpoint?

a) Na+, C2H3O2−, OH−, and H2O

b) Na+, C2H3O2−, HC2H3O2, OH−, and H2O

c) Na+, HC2H3O2, OH−, and H2O

d) Na+, C2H3O2−, H3O+, and H2O

e) Na+, HC2H3O2, H3O+, and H2O

21. In the titration lab, the student is supposed to dissolve the solid acid in 50.0 mL of water. How would the amount of base needed change if 100. mL of water was used instead?

a) increase greatly d) decrease slightly

b) increase slightly e) decrease greatly

c) not change

Answers to Practice Test:

|1. | |11. | |

|2. | |12. | |

|3. | |13. | |

|4. | |14. | |

|5. | |15. | |

| | | | |

|6. | |16. | |

|7. | |17. | |

|8. | |18. | |

|9. | |19. | |

|10. | |20. | |

| | |21. | |

| | | | |

| | | | |

| | | | |

| | | | |

| | | | |

Answers to Practice Test:

|1. |D |11. |C |

|2. |A |12. |B |

|3. | |13. |D |

|4. | |14. |A |

|5. |A |15. |D |

| | | | |

|6. |D |16. |A |

|7. |D |17. |A |

|8. |C |18. |E |

|9. |A |19. |C |

|10. |A |20. |B? |

| | |21. |C |

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