7.19.1: Solutions (Exercises)
- Page ID
- 291716
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Exercises selected from the following sources. Some questions have been modified and/or added by Kristina Novek
· Textmap created for Chemistry: A Molecular Approach by Nivaldo Tro.
· Sacramento City College, CHEM 309: General, Organic and Biochemistry Prof. Dianne Bennett
· Textmap created for "Principles of Modern Chemistry" by Oxtoby et al.
· Chapter 11 Solutions and Colloids (Exercises) Contributed by Paul Flowers, Klaus Theopold & Richard Langley et al. General Chemistry at OpenStax CNX
· Chapter 9 Book: The Basics of GOB Chemistry (Ball et al.)
· Complementary General Chemistry question banks can be found for other Textmaps and can be accessed here.
Water, Solutions, & Electrolytes
1. Identify if the statements about the properties of water are true or false.
a) Ice floats in liquid water because of its lower density
b) Water contains oxygen atoms with a slight positive charge
c) Water is considered a nonpolar molecule
d) Hydrogen bonding creates high surface tension
2. Identify each as either an example of (a) gas in a liquid, (b) gas in a gas, (c) solid in a solid, or (d) liquid in a liquid.
I. bronze (solution of tin or other metals in copper)
II. O2 in N2 (air)
III. CO2 in water
3. Predict whether each of the following substances would be more soluble in water (polar solvent) or in a hydrocarbon such as heptane (C7H16, nonpolar solvent):
a) vegetable oil (nonpolar)
b) isopropyl alcohol (polar)
c) potassium bromide (ionic)
4. Explain why the ions Na+ and Cl− are strongly solvated in water but not in hexane, a solvent composed of nonpolar molecules.
5. Explain why solutions of HBr in benzene (a nonpolar solvent) are nonconductive, while solutions in water (a polar solvent) are conductive.
6. What is the expected electrical conductivity of the following solutions?
a) NaOH(aq)
b) HCl(aq)
c) C6H12O6(aq) (glucose)
d) NH3(l)
7. Answer the following True or False statements.
a) In a solution, the solvent is the substance being dissolved
b) An electrolyte is another word for molecule
c) A solution is a pure substance
d) Homogenous is the best way to describe a solution
e) A solute is all that is needed to make a solution
8. Of the following examples of solutions, determine whether the solute is an electrolyte or a molecule.
a) Plain soda (carbonated) water
b) Apple juice from concentrate
c) A bottle of rubbing alcohol (2-propanol)
d) A saline solution of KCl
9. It is important to distinguish between the solute and the solvent. For each example that is a solution, identify which substance is the solute and which is the solvent.
a) carbonated water
b) a saline solution of sodium chloride
c) sugar water for a bird feeder
d) a sodium bicarbonate buffer solution
e) oxygen in air
Solubility
1. Define solubility. Do all solutes have the same solubility?
Solubility of Solids in Water
2. Use the solubility graph above to answer the following questions.
a) At what temperature is a 60 gram, KBr solution saturated?
b) If 140 grams of NaBr was added to 100 g of water at 400C, how much would not dissolve?
c) If 15 grams of KCl was added to 100 g of water at 250C would the solution be saturated or unsaturated?
d) A solution of KNO3 contained 50 grams at 70 0C. How many additional grams of KNO3 would have to be added to create a saturated solution?
e) A solution of KBr contains 40 grams of KBr in only 50 grams of water. The temperature of the solution 200C. Is the solution saturated or unsaturated?
f) If a solution containing 115 grams of NaNO3 was cooled from 900C to 200C, how much would precipitate out (assuming a supersaturate solution did not form)?
3. Which of the following would allow a greater amount of carbon dioxide to dissolve in water?
a) Decrease the temperature
b) Increase the temperature
c) Add a catalyst
d) Decrease the pressure
Concentration
1. Explain why the terms dilute or concentrated are of limited usefulness in describing the concentration of solutions.
Table Retrieved from:Chapter 9 Section 9.2 Concentration Book: The Basics of GOB Chemistry (Ball et al.)
2. Use the data from the above table to answer the following questions.
a) Calculate the mass/mass percent of a saturated solution of NaCl. Assume that masses of the solute and the solvent are additive and use the density of H2O (1.00 g/mL) as a conversion factor.
b) Calculate the mass/mass percent of a saturated solution of MgCO3. Assume that masses of the solute and the solvent are additive and use the density of H2O (1.00 g/mL) as a conversion factor.
3. Only 1.36 mL of C6H6 will dissolve in 100.000 mL of H2O. Assuming that the volumes are additive, find the volume/volume percent of a saturated solution of benzene in water.
4. Only 35 mL of aniline (C6H5NH2) will dissolve in 1,000 mL of H2O. Assuming that the volumes are additive, find the volume/volume percent of a saturated solution of aniline in water.
5. A solution of ethyl alcohol (C2H5OH) in water has a concentration of 20.56% v/v. What volume of C2H5OH is present in 255 mL of solution?
6. What mass of KCl is present in 475 mL of a 1.09% m/v aqueous solution?
7. The average human body contains 5,830 g of blood. What mass of arsenic is present in the body if the amount in blood is 0.55 ppm?
8. The Occupational Safety and Health Administration has set a limit of 200 ppm as the maximum safe exposure level for carbon monoxide (CO). If an average breath has a mass of 1.286 g, what is the maximum mass of CO that can be inhaled at that maximum safe exposure level?
9. Which concentration is greater—15 ppm or 1,500 ppb?
10. Express the concentration 7,580 ppm in parts per billion.
11. What is the molarity of 0.500 L of a potassium chromate solution containing 0.0650 mol of K2CrO4?
12. What is the molarity of 4.50 L of a solution containing 0.206 mol of urea [(NH2)2CO]?
13. What is the molarity of a 2.66 L aqueous solution containing 0.96 moles of NaBr?
14. If 3.08 moles of Ca(OH)2 is dissolved in enough water to make 0.875 L of solution, what is the molarity of the Ca(OH)2?
Precipitates
1. Rewrite the following balanced equations as net ionic equations.
a) 2Na3PO4(aq) + 3CaCl2(aq) → 6NaCl(aq) + Ca3(PO4)2(s)
b) BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)
c) 2AgNO3(aq) + ZnCl2(aq) → 2AgCl(s) + Zn(NO3)2(aq)
2. When the following solutions are mixed, does a precipitate form? Write out the total molecular, total ionic, and net ionic equations.
a) lead (II) nitrate and potassium chloride
b) magnesium nitrate and calcium chloride
c) calcium chloride and sodium carbonate