physical behavior of matter

physical behavior of matter.....aim 4
what is a solution?
.....aim 3	home	aim 5.....

MU #1 A solution is a homogeneous mixture of a solute dissolved in a solvent.

The solvent is generally in excess.

Example

The solution NaCl(aq) is sodium chloride NaCl(s) dissolved in water H₂O(l)

The solute is NaCl(s) and the solvent is H₂O(l)

MU #2 The solubility of a solute in a given amount of solvent is dependent on the temperature, the pressure, and the chemical natures of the solute and solvent.

Temperature

In general, as the temperature of a solution increases the solubility increases. See table G

Pressure

The solubility of a gas increases as the pressure increases.

Example

Carbon dioxide, CO₂(g) in carbonated drinks is dissolved in the solvent by increasing the pressure and also decreasing the temperature.

Chemical natures of the solute and solvent

A polar solute will dissolve in a polar solvent but not in a nonpolar solvent. The adage "like dissolves like" is very useful.

Example

Alcohol (polar substance) dissolves in water (polar substance)

Water (polar substance) does not dissolve in oil (nonpolar substance)

Solubility curve

See table G

Any point on a line represents a saturated solution.

In a saturated solution, the solvent contains the maximum amount of solute.

Example

At 90^oC, 40 g of NaCl(s) in 100g H₂O(l) represent a saturated solution.

Any point below a line represents an unsaturated solution.

In an unsaturated solution, the solvent contains less than the maximum amount of solute.

Example

At 90^oC, 30 g of NaCl(s) in 100g H₂O(l) represent an unsaturated solution. 10 g of NaCl(s) have to be added to make the solution saturated.

Any point above a line represents a supersaturated solution.

In a supersaturated solution, the solvent contains more than the maximum amount of solute. A supersaturated solution is very unstable and the amount in excess can precipitate or crystallize.

Example

At 90^oC, 50 g of NaCl(s) in 100g H₂O(l) represent a supersaturated solution. Eventually, 10 g of NaCl(s) will precipitate.

Any solution can be made saturated, unsaturated, or supersaturated by changing the temperature.

TEST YOUR UNDERSTANDING

6/02

According to Reference Table G, which solution is saturated at 30^oC?

(1) 12 grams of KClO₃ in 100 grams of water (3) 30 grams of NaCl in 100 grams of water

(2) 12 grams of KClO₃ in 200 grams of water (4) 30 grams of NaCl in 200 grams of water

8/02

One hundred grams of water is saturated with NH₄Cl at 50^oC. According to Table G, if the temperature is lowered to 10^oC, what is the total amount of NH₄Cl that will precipitate? (1) 5.0 g (2) 17 g (3) 30. g (4) 50. g

1/03

1 Solubility data for four different salts in water at 60^oC are shown in the table below.

Which salt is most soluble at 60^oC? (1) A (2) B (3) C (4) D

2 Base your answers on the information below. When cola, a type of soda pop, is manufactured, CO₂(g) is dissolved in it.

1. A capped bottle of cola contains CO₂(g) under high pressure. When the cap is removed, how does pressure affect the solubility of the dissolved CO₂(g)?

2. A glass of cold cola is left to stand 5 minutes at room temperature. How does temperature affect the solubility of the CO₂(g)?

3. Draw a set of axes and label one of them "Solubility” and the other "Temperature."

4. Draw a line to indicate the solubility of CO₂(g) versus temperature on the axes drawn in part a.

1/04

11 Which must be a mixture of substances? (1) solid (2) liquid (3) gas (4) solution

Base your answers to questions 56 through 58 on the information below.
A student uses 200 grams of water at a temperature of 60°C to prepare a saturated solution of potassium chloride, KCl.

56 Identify the solute in this solution.
57 According to Reference Table G, how many grams of KCl must be used to create this saturated solution?

58 This solution is cooled to 10°C and the excess KCl precipitates (settles out). The resulting solution is saturated at 10°C. How many grams of KCl precipitated out of the original solution?

6/04

Base your answers to questions 71 through 74 on the data table below, which shows the solubility of a solid solute.

71 Graph the data from the data table . Circle and connect the points.

73 Based on the data table, if 15 grams of solute is dissolved in 100 grams of water at 40°C, how many more grams of solute can be dissolved in this solution to make it saturated at 40°C?

74 According to Reference Table G, how many grams of KClO₃ must be dissolved in 100 grams of H₂O at 10°C to produce a saturated solution?

8/04

13 At room temperature, the solubility of which solute in water would be most affected by a change in pressure?

(1) methanol (l) (2) sugar (s) (3) carbon dioxide (g) (4) sodium nitrate (s)

1/05

15 A sample is prepared by completely dissolving 10.0 grams of NaCl in 1.0 liter of H₂O. Which classification best describes this sample?

(1) homogeneous compound (2) homogeneous mixture (3) heterogeneous compound (4) heterogeneous mixture

Two alcohols that are used in our everyday lives are rubbing alcohol and ethylene glycol. Rubbing alcohol is used as an antiseptic. Ethylene glycol is the main ingredient in antifreeze, which is used in automobile cooling systems.

77 Explain, in terms of molecular polarity, why rubbing alcohol, 2-propanol, is soluble in water.

6/05

14 The solubility of KClO3(s) in water increases as the

                    (1) temperature of the solution increases (2) temperature of the solution decreases

                    (3) pressure on the solution increases (4) pressure on the solution decreases

41 According to Reference Table G, which substance forms an unsaturated solution when 80 grams of the substance is dissolved in 100 grams of H₂O at 10°C?

                    (1) KI          (2) KNO₃         (3) NaNO₃        (4) NaCl

1/06

14 A mixture of crystals of salt and sugar is added to water and stirred until all solids have dissolved. Which statement best describes the resulting mixture?

(1) The mixture is homogeneous and can be separated by filtration. (2) The mixture is homogeneous and cannot be separated by filtration.

(3) The mixture is heterogeneous and can be separated by filtration. (4) The mixture is heterogeneous and cannot be separated by filtration.

41 A student adds solid KCl to water in a flask. The flask is sealed with a stopper and thoroughly shaken until no more solid KCl dissolves. Some solid KCl is still visible in the flask. The solution in the flask is

(1) saturated and is at equilibrium with the solid KCl (2) saturated and is not at equilibrium with the solid KCl

(3) unsaturated and is at equilibrium with the solid KCl (4) unsaturated and is not at equilibrium with the solid KCl

Base your answers to questions 68 through 70 on the information and table below.

A student conducts an experiment to determine how the temperature of water affects the rate at which an antacid tablet dissolves in the water. The student has three antacid tablets of the same size and composition. The student drops one tablet into each of three beakers containing 200. milliliters of water at different temperatures and measures the time it takes for each tablet to completely dissolve. The results are shown in the table below.

68 Describe the effect of water temperature on the rate of dissolving.

69 Explain, in terms of collision theory, how water temperature influences the rate of dissolving.

70 What change, other than temperature, would affect the rate of dissolving?

6/06

40 A saturated solution of NaNO3 is prepared at 60.°C using 100. grams of water. As this solution is cooled to 10.°C, NaNO3 precipitates (settles) out of the solution. The resulting solution is saturated. Approximately how many grams of NaNO3 settled out of the original solution?

(1) 46 g (2) 61 g (3) 85 g (4) 126 g

Base your answers to questions 67 and 68 on the information below.

The graph shows the relationship between the solubility of a sequence of primary alcohols in water and the total number of carbon atoms in a molecule of the corresponding alcohol at the same temperature and pressure. A primary alcohol has the –OH group located on an end carbon of the hydrocarbon chain.

67 Describe the relationship between the solubility of a primary alcohol in water and the total number of carbon atoms in the primary alcohol.

68 Determine the total mass of 1-pentanol that will dissolve in 110. grams of water to produce a saturated solution.

8/06

41 An unsaturated aqueous solution of NH3 is at 90.°C in 100. grams of water. According to Reference Table G, how many grams of NH3 could this unsaturated solution contain?

(1) 5 g (2) 10. g (3) 15 g (4) 20. g

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