Topics – Solutions
1. Arrhenius Acids and bases
a. An acid increases the H+ concentration in solution b. A base increases the OH- concentration in solution 2. Strong acids and bases completely dissociate
3. Weak acids and bases only dissociate to a small percentage.
4. Acids and bases as electrolytes
5. Neutralization reactions – Acid + base salt + water 6. Autoionization of water
a. H2O H+ + OH-
7. Neutralization reactions – molecular, ionic and net ionic reactions 8. pH and pOH
a. pH = -log [H+] b. pOH = -log [OH-] c. pH + pOH = 14
d. pH scale – acidic, basic and neutral 9. Acid – Base titrations
a. Calculations b. Equivalence point
c. Indicators and end points d. Titrations curves
Multiple Choice
1. Which of these pH numbers
indicates the highest level of acidity?
(1) 5 (3) 10
(2) 8 (4) 12
2. According to the Arrhenius theory, when a base dissolves in water it produces
(1) CO32- as the only negative ion in solution
(2) OH- as the only negative ion in solution
(3) NH4+ as the only positive ion in solution
(4) H+ as the only positive ion in solution
3. Which solution when mixed with a drop of bromthymol blue will cause the indicator to change from blue to yellow?
(1) 0.1 M HCl (3) 0.1 M CH3OH (2) 0.1 M NH4OH (4) 0.1 M NaOH
4. What is the pH of a solution containing 20 grams of NaOH in 1000 milliliters of solution?
(1) 0.30 (3) – 0.30 (2) 13.70 (4) –13.70
5. What is the pH of a solution whose H+ concentration is 1.5 M?
(1) – 0.18 (3) –13.82 (2) 0.18 (4) 13.82 6. A solution whose pH is 8.9 is
(1) Acidic (2) Basic (3) Neutral
7. A student neutralized 16.4 milliliters of HCl by adding 12.7 milliliters of a 0.620 M KOH solution. What was the molarity of the HCl solution?
(1) 0.168 M (3) 0.620 M (2) 0.480 M (4) 0.801 M
8. When the pH of a solution changes from a pH of 5 to a pH of 3, the hydrogen ion concentration is
(1) 0.01 of the original content (2) 0.1 of the original content (3) 10 times the original content (4) 100 times the original content
9. A sample of Ca(OH)2 is considered to be an Arrhenius base because it dissolves in water to yield
(1) Ca2+ ions as the only positive ions in solution
(2) H3O+ ions as the only positive ions in solution
(3) OH- ions as the only negative ions in solution
(4) H- ions as the only negative ions in solution
10. Which reaction occurs when hydrogen ions react with hydroxide ions to form water?
(1) substitution (3) ionization (2) saponification (4) neutralization
11. Which equation represents a double replacement reaction?
(1) 2 Na + 2 H2O 2 NaOH + H2
(2) CaCO3 CaO + CO2
(3) LiOH + HCl LiCl + H2O (4) CH4 + 2 O2 CO2 + 2 H2O
12. Which of the following acids is a weak electrolyte?
(1) HF (3) HNO3
(2) HCl (4) HClO4
13. Which of these 1 M solutions will have the highest pH?
(1) NaOH (3) HCl
(2) CH3OH (4) NaCl 14. Given the following solutions”
Solution A: pH of 10 Solution B: pH of 7 Solution C: pH of 5
Which list has the solutions placed in order of increasing H+ concentration?
(1) A, B, C (3) C, A, B (2) B, A, C (4) C, B, A
15. A compound whose aqueous solution conducts electricity and turns
phenolphthalein pink is
(1) HCl (3) NaOH
(2) HC2H3O2 (4) CH3OH
16. Which of the following is a polyprotic acid?
(1) NH3 (3) H3PO4
(2) HCl (4) CH4
17. Which of the following is a weak base?
(1) ammonia
(2) sodium chloride (3) calcium hydroxide (4) sodium hydroxide
18. Which of the following solutions would cause methyl orange to be red?
(1) 0.10 M HCl (2) 0.010 M NaOH (3) 0.0010 M Ca(OH)2
(4) 0.000010 M HNO3
19. Which of the following, when dissolved in water would produce a neutral solution?
(1) vitamin C (2) phosphoric acid (3) sodium chloride (4) potassium hydroxide
20. Which substance is an Arrhenius acid?
(1) LiF (aq) (3) Mg(OH)2 (aq) (2) HBr (aq) (4) CH3CH2OH (aq)
Short Answers
Calcium hydroxide is commonly known as agricultural lime and is used to adjust soil pH. Before lime was added to a field, the soil pH was 5. After the lime was added, the soil underwent a 100-fold decrease in the hydrogen ion concentration.
21. What is the new pH of the soil in the field?
22. Calcium hydroxide is relatively soluble in water. Give the formula and name of another hydroxide compound that contains a Group 2.
23. Calculate the pH of the following solutions. You must show work to receive full credit.
(a) 0.10 M HCl
(b) 0.010 M NaOH
(c) a 0.35 M solution of a weak acid that dissociate 2%.
(d) a 0.15 M solution of a weak base that dissociate 10%.
24. If an acid is added to an aqueous solution, briefly describe what happens to the pH and pOH of the solution as compared with the original pH and pOH of the
solution.
25. A student recorded the following buret readings during a titration of 25.0 mL of a potassium hydroxide solution with unknown concentration with hydrochloric acid:
Standard 0.100 M hydrochloric acid Initial reading 9.08 mL Final Reading 19.09 mL a. Write the balanced neutralization reaction.
b. Calculate the molarity of the potassium hydroxide solution. Show all work.
26. Draw a plot of the titration curve of a 0.10 M hydrochloric acid solution is titrated with sodium a 0.10 M NaOH solution. Be sure to:
(a) Put the pH on the y-axis and mL of NaOH added on the x-axis.
(b) Use appropriate scales and label the axes.
(a) Start the titration at the initial pH of the HCl solution
(b) Label the equivalence point and make sure that it occurs at the appropriate pH and added volume of NaOH for this titration
(c) Select an indicator from the reference table that could be used for the end point of this titration.
(d) Write the balanced neutralization reaction
Answers
1. 1 2. 2 3. 1 4. 2 5. 1 6. 2 7. 2 8. 4 9. 3 10. 4 11. 3 12. 1 13. 1 14. 1 15. 3 16. 3 17. 1 18. 1 19. 3 20. 2
21. the pH = 7
22. Sr(OH)2 or Ba(OH)2
23. (a) pH = 1.0 (b) pH = 12.0 (c) pH = 2.2 (d) pH = 12.2
24. The pH will go down and the pOH will go up.
25. (a) KOH (aq) + HCl (aq) KCl (aq) + H2O (l); (b) 0.0400 M 26. Show your teacher.
