6.8: End of Chapter Problems
Classification of Matter
1. Identify each substance as a compound, an element, a heterogeneous mixture, or a homogeneous mixture (solution).
a. filtered tea
b. freshly squeezed orange juice
c. aluminum oxide, Al 2 O 3
d. selenium
e. white wine
f. mercury
g. ranch-style salad dressing
h. table sugar (sucrose)
2. What category does each example of matter (solid/liquid/gas) belong to?
a. saltwater
b. soil
c. water
d. oxygen
e. coffee grounds
f. hydrogen
g. a boiled egg
h. steam
3. Which of the following substances are elements?
sodium
milk
gold
water
air
liquid nitrogen
paper
electricity
neon
carbon
wood
concrete
Solution and Solubility
1. Water is considered a polar solvent. Which substances should dissolve in water?
a. methanol (CH 3 OH)
b. sodium sulfate (Na 2 SO 4 )
c. octane (C 8 H 18 )
2. Toluene (C 6 H 5 CH 3 ) is widely used in industry as a nonpolar solvent. Which substances should dissolve in toluene?
a. water (H 2 O)
b. sodium sulfate (Na 2 SO 4 )
c. octane (C 8 H 18 )
3. Predict which of the following compounds will be most soluble in water:
Ethanol: CH 3 CH 2 OH or Hexanol: CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 OH
Formic acid: HCOOH or Pentanoic acid: CH 3 CH 2 CH 2 CH 2 COOH
Isopropyl alcohol: CH 3 CH(OH)CH 3 or Propylene glycol: CH 3 CH(OH)CH 2 OH
4. What happens to solubility of carbon dioxide gas (CO 2 ) in water when
a. the temperature is increased.
b. the temperature is decreased.
5. Explain why an opened bottle of carbonated water keeps its fizz longer if kept in a refrigerator than if kept at room temperature.
6. On a hot day, it is often easier to catch fish by casting your line into a deep, cool part of a lake than into a shallow, warm spot. One reason that fish gather in cool water may be related to the levels of oxygen dissolved in the water. Explain.
7. One concern about global warming is that increase in water temperature may lead to the death of many fish. How may this be related to the solubility of O 2 in water?
8. Vitamin D is a water-insoluble vitamin, while vitamin C is water-soluble. Why?
9. Acesulfame-K (shown below) is the potassium salt of acesulfame. Acesulfame-K is used as a artificial sweetener since it has a greater solubility in water compared to acesulfame. Explain why.
Solution Concentration
Use the following relationships in the problems where needed:
1 Liter = 1000 mL
1 gram = 1000 mg
Use the periodic table for formula weight and molecular weight of the compounds.
1. Potassium iodide is used to treat iodine deficiencies. What is the %(w/v) of a 75 mL solution containing 2.0 g KI?
2. A solution is prepared by dissolving 42.23 g of NH 4 Cl into enough water to make 500.0 mL of solution. Calculate its molarity.
2. Calculate the molarity of each:
a. 0.33 mol of NaCl in 2.0 L of solution.
b. 55.0 g of NaCl in 125 mL of solution.
3. Calculate the molarity of each:
a. 1.75 mol of glucose (C 6 H 12 O 6 ) in 15.2 L of solution.
b. 270 mg of glucose in 1.00 mL of solution.
4. If 15.0 g of CaCl 2 is present in 250 mL of aqueous solution, what is the concentration in terms of the following?
a. molarity
b. weight/volume percent
5. If 0.30 mg of sodium fluoride is present in 1.0 L of aqueous solution, what is the concentration in terms of the following?
a. molarity
b. weight/volume percent
6. 100 mL of blood serum contains 5.0 mg of thyroxine, a hormone released by the thyroid gland. What is the weight/volume percent concentration?
Dilutions
1. Nitric acid (HNO 3 ) is a powerful and corrosive acid. When ordered from a chemical supply company, its molarity is 16 M. How much of the stock solution of nitric acid needs to be used to make 8.00 L of a 0.50 M solution?
2. You have a 0.50 L of a 0.24 M aqueous glucose solution. You add enough water to give a final volume of 1.0 L. What is the new concentration?
3. You begin with 25 mL of a 1.8 M aqueous LiCl solution and add enough water to a final volume of 350 mL. What is the new concentration?
4. A 5.0% (w/v) solution of ethyl alcohol is diluted from 50.0 mL to 75.0 mL. What is the new weight/volume percent?
5. Calculate the final volume required to prepare 0.020 % (w/v) KI starting with 10. mL of 2.0% (w/v) KI.
Osmosis and Diffusion
1. Define the terms osmosis and diffusion
2. What do the terms isotonic, hypertonic and hypotonic mean?
3. What is crenation and hemolysis? Why do they happen?
4. To make pickles, you soak cucumbers in a concentrated salt solution called brine. Describe how this is related to osmosis.
5. Pickled cucumber tastes salty. Describe how this is related to diffusion.
6. The hypertonic solution made from dissolving Epsom salt (MgSO 4 ) is used as a home remedy that can help reduce the swelling and discomfort of hemorrhoids.
a. How does this hypertonic solution reduce the swelling?'
b. Will pure water have the same effect? Explain.
7. Why is it important for dialyzing solution to be isotonic with blood?
8. Explain the process of hemodialysis.