Name:______
Grade 11B/G Take Home Test
Due Friday April 15, 2011
Acids, Bases and Solubility
Instructions:
· Please answer each of the following questions in the space provided.
· Test will be marked out of 100; each question is worth 5 marks
· 5 marks will be deducted per day late.
· There will be no bonus questions.
And so, let me be clear, all explanations are expected to be delivered in English!
1. Define each of the following:
a) Arrhenius base
b) Brønsted-Lowry acid
d) Turning point and equivalence point
2. Complete the table below knowing that a newly created indicator HA-Chemblue has a turning point of 6 (Green to blue). (no decimal exponents allowed!)
[H+], M / [OH-], M / pH / pOH / Acid or base / Color2.35 x 10-2
2.35 x 10-2
2.35
2.35
Show work for 1st row only:
3. When 0.1 mole of acetic acid (CH3COOH) is dissolved in 1L of water, the pH is found to be 3. Find the Ka of acetic acid. What is the % ionization of this acid?
The reaction for the dissociation of acetic acid is:
CH3COOH ↔ CH3COO- (aq) + H+ (aq)
4. If the Ka of an acid, HA, is 3 x 10-5, find the pH of a 0.15M solution of this acid. What is the percent ionization of this acid?
5. 9.405g of an organic acid (HX, molecular weight of 188.1g/mole) is dissolved in 500ml water. If 100ml of this acid neutralize 76.3ml of an NaOH solution, what is the concentration of the NaOH solution?
6. Given the following balanced ionization reactions for the following weak acids and bases, write the Ka or Kb expressions for each.
a. / ascorbic acid: HC6H7O6 (aq) ÛH+(aq) + C6H7O6-(aq) / Ka =b. / boric acid: H3BO3 (aq) Û H+(aq) + H2BO3- (aq) / Ka =
c. / methyl amine: CH3NH2 (aq) + H2O(l) Û CH3NH3+(aq) + OH- (aq) / Kb =
7. Calculate [OH-] is a solution containing 100.0 g of potassium hydroxide in 2.50 L solution. Potassium hydroxide is a strong base.
8. A solution is prepared the contains 0.0445 mole of sulfuric acid in a total solution volume of 12.1 L. Sulfuric acid typically undergoes complete ionization according to the equation:
H2SO4 ® 2H+ + SO42-
Calculate [H+]. Sulfuric acid is a strong acid.
9. Calculate both [H+] and [OH-] for the following solutions. All are either strong acids or strong bases. Be sure to clearly identify all answers.
a) 2.5 M NaOH
b) 0.045 M HCl
10.A 2.67 g sample of hydrogen fluoride gas (HF) is dissolved in sufficient water to make 1.05 L of solution at 25°C to form an acidic solution. Hydrogen fluoride is a weak acid with Ka = 6.6 ´ 10-4. Calculate the pH of this solution.
11. The formula for ascorbic acid, better known as Vitamin C, is HC6H7O6. Ka for ascorbic acid is 8.00 ´ 10-5. Determine the pH of a solution prepared by dissolving a 500.0 mg vitamin C tablet in enough water to make 200.0 mL of solution.
12. A neutral solution is produced when 42.00 mL of a 0.150 M NaOH solution is used to titrate 50.00 mL of a sulfuric acid (H2SO4) solution. What is the concentration of the sulfuric acid solution before titration?
H2SO4 + 2 NaOH Û Na2SO4 + 2 H2O
13. Morphine (C17H19NO3) is a base of neutral origin used to control pain. A solution of 4.5 x 10-3 M has a pH of 9.93. Calculate the basicity constant of morphine.
14. The concentrations of hydroxide ions (OH-) in a solution of aqueous sodium proprionate (NaC2H5COO) at 0.157M is 1.1 x 10-5mol/L. Calculate the basicity constant of sodium proprionate.
15. The maximum solubility of silver cyanide (AgCN) is 1.5 x 10-8M at 25˚C. Calculate the value of the solubility constant of silver cyanide.
16. Based on the degree of dissociation, what is the difference between a strong acid and a weak acid and between a strong base and a weak base?
17. Butanoic Acid (C4H8O2) also called butyric acid, gives fresh parmesan cheese its characteristic odor. Calculate the pH of a solution at 1.0 x 10-2mol/L of butanoic acid if the value of its acidity constant is 1.51 x 10-5.
18. Draw and label the curve for the titration of 100ml of 0.15M NaOH with 1.3M H2SO4.
19. Determine the final pH of each of the following mixtures.
a) 50ml 0.2M HCl with 150ml 1.3M NaOH
b) 50ml 0.2M HCl with 150ml 1.3M Ba(OH)2
c) 50ml 0.2M H3PO4 with 150ml 1.3M NaOH
d) 50ml 0.2M H2SO4 with 150ml 1.3M Ca(OH)2
20. Ammonia (NH3) dissolves in water to form ammonium hydroxide (NH4OH) according to the following equation:
NH3 (aq) + H2O (l) Û NH4+(aq) + OH-(aq)
The value of the basicity constant of ammonia at 25˚C is 1.8 x 10-5. What is the pH of an ammonium hydroxide solution at 0.40mol/L? (Do not include H2O(l) in your calculations).
21. Calculate the pH of an aqueous solution of formic acid (HCOOH) at 0.20mol/L if the value of its acidity constant is 1.8 x 10-4, given that:
HCOOH(aq) ÛH+(aq) + HCOO-(aq)
22. The maximum solubility of Barium Fluoride (BaF2) at 25˚C is 1.3g/L.
a) Calculate the value of the solubility product constant of BaF2 at 25˚C.
b) Calculate the solubility of BaF2 in molecules per liter.
c) Why is the temperature always included in the statement of solubility values?
23. Determine the mass of sodium hydroxide (NaOH) that must be dissolved to obtain 2L of a solution with a pH of 10.35.
24. 8.5 g NaOH is dissolved in 500ml of a cleaning solution. Determine the pH of the solution.
25. Use the information in the table below to determine which acid is the weakest and which is the strongest. You must show all your work. Note: Relative strength is not based on pH alone.
Acid / Initial Concentration / pHA / 0.10 / 3.0
B / 0.000010 / 6.9
C / 0.010 / 3.6
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