Name: ______
SCH3U Unit 4 Test – Solutions and Solubility
E2. (21 marks total) Part 1. Multiple choice: circle the correct answer. (1 mark each)
1. If solutions of potassium chloride and silver nitrate are mixed, which of the following are spectator ions?
a. / Ag+ and Cl– / d. / K+ and NO3–b. / K+ and Cl– / e. / none of the above
c. / Ag+ and NO3–
2. Which of the following is the correct dissociation reaction for calcium hydroxide?
a. / Ca(OH)2(s) → Ca2+(aq) + 2OH–(aq)b. / CaOH(s) → Ca+(aq) + OH–(aq)
c. / Ca(OH)2(s) → 2Ca2+(aq) + OH–(aq)
d. / Ca(OH)3(s) → Ca3+(aq) + 3OH–(aq)
e. / Ca(OH)2(s) → 2 Ca2+(aq) + 2OH–(aq)
3. What volume of a 10.00 mol/L stock solution is needed to make 500 mL of 0.45 mol/L solution?
a. / 0.0225 mL / d. / 225 mLb. / 111.1 mL / e. / 22.5 mL
c. / 2.25 mL
4. 25.4 g of salt was dissolved in distilled water to make 425 mL of solution. What is the percent m/v concentration?
a. / 94.0% / d. / 4.25%b. / 25.4% / e. / 2.54%
c. / 5.98%
5. A student dissolved 0.515 mol of magnesium chloride in enough water to make 225 mL of solution. What is the molar concentration of the chloride ion in solution?
a. / 2.29 mol/L / d. / 4.58 mol/Lb. / 0.00229 mol/L / e. / 0.44 mol/L
c. / 0.00458 mol/L
Part 2. Short answer (Show your work by using the GREAT method)
1. For the following reaction, write the total ionic equation and the net ionic equation. (3 marks)
Na2SO4 (aq) + Sr(OH)2 (aq) à SrSO4 (s) + 2 NaOH (aq)
Total Ionic: 2 Na+ (aq) + SO42- (aq) + 2 OH- (aq) + Sr2+ (aq) à SrSO4 (s) + 2 Na+ (aq) + 2 OH- (aq)
Net ionic: Sr2+ (aq) + SO42- (aq) à SrSO4 (s)
2. T.S.P is an all-purpose cleaner that can be used to clean driveways. What volume of solution would you get if you dissolved 150.0 g of sodium phosphate with water to produce a 0.23 mol/L solution? (3 marks)
1 – MM Na3PO4 = 163.94 g/mol
1 – n = m/ MM = 150.0 g/163.94 g/mol = 0.915 mol
1 – C = n/v => v = n/c 0.915 mol/0.23 mol/L = 3.98 L
3. Since 1991, house paint produced in Canada must contain less than 600 ppm of lead. What is the maximum mass of lead permitted in a can that contains 7000 g of paint? (2 marks)
1 => g solute / g solvent * 106 = ppm
1=> g solute = ppm X g solvent / 106 = 600 * 7000 g / 106 = 4.2 g
4. Coffee has a pH of 5.0 and grapefruit juice has a pH of 3.0.
a. Calculate the hydrogen ion concentration for both drinks. (2 marks)
b. How many times more concentrated are the hydrogen ions in the juice compared to the coffee? (1 mark)
a) coffee: 1X10-5 mol/L, grapefruit juice: 1X10-3 mol/L
b) 100X
5. Sodium sulfate reacts with barium chloride to produce a precipitate. The sodium sulfate solution has a molar concentration of 0.175 mol/L and the barium chloride solution has a concentration of 0.245 mol/L. Only 100.0 mL of barium chloride is used. Calculate the volume of sodium sulfate needed to fully react with the barium chloride. (5 marks)
1 – balanced chemical equation:
Na2SO4 (aq) + BaCl2 (aq) à 2 NaCl (aq) + BaSO4 (s)
1 – moles of BaCl2 n = CXV = 0.1 L * 0.245 mol/L = 0.0245 mol
1 – mole ratio barium chloride to sodium sulfate 1:1
1 – v=n/c =0.0245 mol/ 0.175 mol/L
1 - = 0.140 L or 140 mL
E3. (14 marks) Part 1. Multiple choice: circle the correct answer. (1 mark each)
1. Which of the following is a liquid in gas type of solution?
a. / carbon dioxide in water / d. / vinegarb. / water in air / e. / oil in water
c. / alcohol in water
2. The parts of a water molecule that surround the sodium ions when salt dissolves are the
a. / positive hydrogen ends / d. / positive oxygen endsb. / negative hydrogen ends / e. / chloride ions
c. / negative oxygen ends
3. A solution that contains the maximum quantity of a solute at a specific temperature is
a. / saturated / d. / dissolvedb. / unsaturated / e. / none of the above
c. / supersaturated
4. Intermolecular forces are
a. / forces among molecules / d. / forces within moleculesb. / covalent bonds / e. / none of these
c. / ionic bonds
5. The pH scale measures
a. / the level of saltiness of a solution / d. / concentration of H+(aq) ionsb. / concentration of OH–(aq) ions / e. / none of the above
c. / concentration of acids
Part 2. Short answer
1. What is an acid? (1 mark)
A substance that dissociates in water to produce one or more hydrogen ions, H+ (aq)
2. A 0.1 mol/L solution of nitric acid has a pH of about 1 and a 0.1 mol/L solution of acetic acid has a pH of about 3.
a. Which acid is more acidic? (1 mark)
b. Use percent ionization to explain why these acids have different pH values. (2 marks)
a) Nitric acid -> lower pH
b) nitric acid is a strong acid – 100% ionized – all H+ (aq) free to move around
acetic acid is a weak acid – 50% ionized – Not all the H+ dissociated so not all hydrogens in solution.
3. a. Why is sugar, C12H22O11, soluble in water? (1 marks)
b. Explain how sugar dissolves in water. (2 marks)
1 – polar – has –OHs (oxygens)
2 – the water molecules hydrogen bond to the polar ends on the sugar.
This hydrates the outer sugar molecules and dissolve them in water, leaving inner sugar molecules to be hydrated and dissolved by water.
4. Your classmate is late for his next class and wants to dissolve many big pieces of salt in water very quickly. Give him one suggestion on how he can speed up the process to dissolve his salt and explain to him why this suggestion will work. (2 marks)
1 – idea – agitation or increased temperature or surface area
1 – explanation – see course notes on increasing speed of dissolving.
E1. (3 marks) Short answer
1. Chemicals that make their way into our water ways (we call this waste water) can be dangerous for human health if we do not treat our drinking water before using it.
a. Lead is highly toxic. Suggest a way to precipitate lead, Pb2+, from waste water to make the water non-toxic. (1 mark)
Add an anion that would precipitate the lead out of solution. SO42-, OH-, or Br-/Cl-/I-, for example.
b. Why is it important for scientists to find other ways than precipitation to remove nitrate ions, NO3- (aq), from waste water? Why is it important to remove nitrate ions from our drinking water? (2 marks)
1 – nitrate is always soluble – nothing will precipitate it.
1 – answers vary: it will accumulate in our waste water/we would drink it/etc.