Extra Problems for the Web page for Unit 11: Acids & Bases.

1a) Determine the pH of a solution with a hydrogen ion concentration of 3.5 x 10-4

b) If a solution has a pH of 4.25, what is the hydrogen ion concentration?

2. Determine the pH of each of the following solutions: (a) 0.20 M HCl , (b) 0.10 M NaOH

3. Find the hydronium ion concentration of 0.1 M CH3COOH solution. Assume Ka = 1.75 x 10-5 for acetic acid.

4. Assuming complete neutralization, calculate the number of mL of 0.025 M H3PO4 required to neutralize 25 mL of 0.030 M Ca(OH)2.

5. Determine the molarity of an H2SO4 solution, 15.0 mL of which is completely neutralized by 26.5 mL of 0.100 M NaOH.

The following problems are for Honors only:

6. Find the degree of ionization of 0.05 M NH3 in a solution of pH 11.0. Kb = 1.76 x 10-5

7. What is the pH of a 1.0 M solution of sodium acetate? (Ka = 1.8 x 10-5 for CH3COOH)

8. A lab technician prepared a calcium hydroxide solution by dissolving 1.48 g of Ca(OH)2 in water. How many mL of 0.125 M HCl solution would be required to neutralize this solution?

9. A laboratory technician has a solution of 0.1 M NaCH3COO. Find its pH and the percent hydrolysis.

10. Find the pH of a 0.2 M solution of formic acid, HCOOH. Ka = 1.76 x 10-4

11. 100. mL of 0.1 M NaOH is mixed with 100. mL of 0.15 M CH3COOH. What is the pH of this mixture? .

12. Find the pH of a 0.1 M solution of ammonia, NH3. (Kb = 1.76 x 10-5) .

13. Find the pH of a 0.10 M CH3COOH solution that has 0.20 M NaCH3COO dissolved in it.

14. What is the pH of 0.500 M NaHSO3?

15. Calculate the pH of a 0.25 M solution of the salt ethylamine hydrochloride, C2H5NH3Cl. Kb for C2H5NH2 is 5.6 x 10-4.

Answers: 1(a) 3.46 , 1(b) 5.6 x 10-5 M , 2(a) 0.7 , 2(b) 13 , 3. 0.0013 M , 4. 20. mL , 5. 0.088 M , 6. 1.76% , 7. 9.4 , 8. 320 mL , 9. 8.9 ; 0.0075% , 10. 2.23 , 11. 5.06 , 12. 11.12 , 13. 5.06 , 14. 12.9 , 15. 5.7

The following is an example of an Honors test for Acids & Bases(I):

Multiple Choice:

1. For a solution to be classified as acid, the

a) hydrogen ion concentration must be 1.0 x 10-7 M (b) hydrogen ion and hydroxide ion concentrstions must be equal (c) hydrogen ion concentration must be greater than the hydroxide ion concentration (d) hydrogen ion concentration must be 7 M or greater.

2. The pH of a solution in which [OH-] = 1.0 x 10-4 M is:

a) 4.0 (b) 10.0 (c) -4.0 (d) -10.0

3. In the reaction CO3-2 + H2O <---> HCO3- + OH- , the carbonate ion is acting as a(n)

a) Arrhenius base (b) Arrhenius acid (c) Bronsted-Lowry base (d) Bronsted-Lowry acid

4. According to the Bronsted-Lowry theory, an acid is

a) a proton donor only (b) a proton acceptor only (c) a proton donor and a proton acceptor (d) neither a proton donor nor a proton acceptor

5. Given the equation:

H2O + HF <---> H3O+ + F-

Which pair represents Bronsted-Lowry acids?

a) HF and F- (b) HF and H3O+ (c) H2O and F- (d) H2O and H3O+

6. Which equation illustrates amphoterism?

a) NaCl ---> Na+ + Cl- (b) NaOH ---> Na+ + OH- (c) H2O + H2O <---> H3O+ + OH- (d) HCl + H2O ---> H3O+ + Cl-

7. An aqueous solution of which substance will change red litmus to blue?

a) HCl (b) NaCl (c) CH3OH (d) NaOH

8. Which set of reactants does not produce a gas as one of the products?

a) HCl(aq) + Zn(s) (b) HCl(aq) + Mg(s) (c) HCl(aq) + CaCO3(s) (d) HCl(aq) + Cu(s)

9. The ionization constant (Ka) of HF is 6.7 x 10-4. Which of the following is true in a 0.1 M solution of this acid?

a) [HF] is greater than [H+][F-] (b) [HF] is less than [H+][F-] (c) [HF] is equal to [H+][F-] (d) [HF] is equal to {H+] + [F-]

10. For the reaction HX<---> H+ + X- the equilibrium concentrations are as follows:

[HX] = 1.0 x 10-1 ; [H+] = [X-] = 1.0 x 10-3. Ka would be

a) 1.0 x 105 (b) 1.0 x 10-10 (c) 1.0 x 10-7 (d) 1.0 x 10-5

11. A solution with a pH of 5.0

a) is basic (b) is neutral (c) has a hydrogen ion concentration of 5.0 M (d) has a hydroxide ion concentration of 1.0 x 10-9 M

12. Which of the following pairs consists of a weak acid and a strong base?

a) sulfuric acid, sodium hydroxide (b) acetic acid, ammonia (c) acetic acid, sodium hydroxide (d) nitric acid, calcium hydroxide

13. Which of the following formulas represent bromic acid and hydrosulfuric acid respectively?

a) HBr and H2S (b) HBrO2 and H2SO4 (c) HBrO3 and H2S (d) HBrO and H2SO4

Problems:

14. Complete each reaction. Identify the Bronsted- Lowry acid-base pairs. Indicate which is favored at equilibrium, the reactant or the products.

a) HSO4- + HS- <---->

b) NH3 + H2O <--->

15. What is the pH of 0.20 M acetic acid which is 2.00% ionized?

16. The Ka of benzoic acid (C6H5COOH) is 6.3 x 10-5. What is the equilibrium concentration of hydrogen ions in a 0.10 M solution of benzoic acid?

Answers: 1 c, 2 b, 3 c, 4 a, 5 b, 6 c, 7 d, 8 d, 9 a, 10 d, 11 d, 12 c, 13 c

14 (a) <--> H2S + SO4-2 ; products favored ; HSO4- is acid1, HS- is base2, H2S is acid2, SO4-2 is base1 (b) <---> NH4+ + OH- ; reactants favored ; NH3 is base1, H2O is acid2, NH4+ is acid1, OH- is base2

15. pH = 2.40

16. [H+] = 2.5 x 10-3 M

The following is an example of an Honors test for Acids & Bases (II):

Multiple Choice:

1. The products of the reaction of one mole of Ca(OH)2 and one mole of H2SO4 are:

a) CaSO4 + H3O+ + H2O (b) CaSO4 + 2H2O (c) CaH2 + H3O+ + OH- (d) CaSO4 + H3O+ + OH-

2. The reaction that takes place when an acid is added to an ammonia/ammonium buffer system is:

a) NH4+ <----> NH3 + H+ (b) NH3 + H+ <----> NH4+ (c) NH4+ + OH- <----> NH4OH (d) NH3 + H2O <----> NH4+ + OH-

3. A water solution of which compound will turn blue litmus red?

a) K2CO3 (b) NH4Cl (c) NaCH3COO (d) KCl

4. The net ionic equation for the reaction of an acid with a base is:

a) H2O ----> H+ + OH- (b) H2O + H3O+ ---> 2H2O + H+ (c) H+ + OH- ---> H2O (d) H2O + H+ ---> H3O+

5. How many mL of 0.20 M NaOH are required to neutralize 30.0 mL of 0.50 M H2SO4?

a) 300 mL (b) 60 mL (c) 75 mL (d) 150 mL

6. Identify the Lewis bases in the following three reactions:

H+ + Cl- <----> HCl

BF3 + NH3 <----> F2BNH3

6H2O + Fe+3 <----> Fe(H2O)6+3

a) H+, NH3 and Fe+3 (b) H2O, BF3 and Cl- (c) Cl-, H2O and NH3 (d) BF3, H+ and H2O

7. A student prepares 0.10 M solutions of each of the compounds listed below. Which solution should have the highest pH value?

a) calcium hydroxide (b) copper(II) hydroxide (c) ammonia (d) sodium fluoride

8. Which set of solutes will form a buffer when dissolved in water to make a liter of solution?

a) 0.2 mole of NaOH with 0.2 mole of HCl (b) 0.2 mole NaCl with 0.2 mole of HNO3 (c) 0.4 mole CH3COOH with 0.4 mole of KCH3COO (d) 0.4 mole of KCl with 0.2 mole of HCl (e) 0.3 mole of KOH with 0.2 mole of HBr

9. Which of the following is a pH value that could result when the salt of a strong acid and a weak base undergoes hydrolysis?

a) 5 (b) 7 (c) 9 (d) 13

10. Lewis defined an acid as

a) a proton acceptor (b) a proton donor (c) an electron pair acceptor (d) an electron pair donor

11. How many moles of potassium hydroxide will be required to completely neutralize 500.0 mL of solution containing 20.25 g of hydrobromic acid?

a) 2.0 moles (b) 0.25 moles (c) 0.50 moles (d) 4 moles

12. Which salt hydrolyzes to form a solution that is basic?

a) KCl (b) NaCl (c) NH4Cl (d) LiNO2

13. With solutions of strong acids and strong bases, the word "strong" refers to

a) molarity (b) solubility (c) degree of ionization (d) buffering action

Problems:

14. Lactic acid (HC3H5O3) is a weak organic acid found in milk and in muscle tissues during strenuous exercise. determine the pH of a solution that contains 25.0 g of lactic acid and 38.0 g of potassium lactate in 500.0 mL of solution (Ka for lactic acid is 1.38 x 10-4).

15. Potassium acid oxalate (a solid acid) can be described as the acid salt formed by the partial neutralization of the diprotic acid, oxalic acid. A student dissolved 0.60 g of KHC2O4 in 55.0 mL of water and determined that 46.2 mL of 0.10 M NaOH was required to reach the endpoint of the titration. Determine the molecular mass of the solid acid. Calculate the student's percent error.

16. In murder-mystery movies, cyanide is introduced into the victim's body in the form of a harmless looking salt, potassium cyanide, a deadly poison. Calculate the pH of a 0.0010 M solution of potassium cyanide. (Ka for HCN = 4.9 x 10-10.

Answers: 1 b, 2 b, 3 b, 4 c, 5 d, 6 c, 7 a, 8 c, 9 a, 10 c, 11 b, 12 d, 13 c

14. pH = 3.9

15. 130. g/mol ; 1.5% error

16. pH = 10.7

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