Chemistry 16.1 Chapter 16 Section 1

Properties of Solutions 16.1 A sinkhole forms when the roof of a cave weakens from being dissolved by groundwater and suddenly collapses. One recorded sinkhole swallowed a house, several other buildings, five cars, and a swimming pool! You will learn how the solution process occurs and the factors that influence the process.

16.1 Solution Formation Solution Formation What factors determine the rate at which a substance dissolves?

the surface area of the dissolving particles 16.1 Solution Formation The compositions of the solvent and the solute determine whether a substance will dissolve. The factors that determine how fast a substance dissolves are stirring (agitation) temperature the surface area of the dissolving particles

A cube of sugar in cold tea dissolves slowly. 16.1 Solution Formation A cube of sugar in cold tea dissolves slowly. Stirring and heating increase the rate at which a solute dissolves. a) A cube of sugar in cold tea dissolves slowly. b) Granulated sugar dissolves in cold water more quickly than a sugar cube, especially with stirring. c) Granulated sugar dissolves very quickly in hot tea.

16.1 Solution Formation Granulated sugar dissolves in cold water more quickly than a sugar cube, especially with stirring. Stirring and heating increase the rate at which a solute dissolves. a) A cube of sugar in cold tea dissolves slowly. b) Granulated sugar dissolves in cold water more quickly than a sugar cube, especially with stirring. c) Granulated sugar dissolves very quickly in hot tea.

Granulated sugar dissolves very quickly in hot tea. 16.1 Solution Formation Granulated sugar dissolves very quickly in hot tea. Stirring and heating increase the rate at which a solute dissolves. a) A cube of sugar in cold tea dissolves slowly. b) Granulated sugar dissolves in cold water more quickly than a sugar cube, especially with stirring. c) Granulated sugar dissolves very quickly in hot tea.

Stirring and Solution Formation 16.1 Solution Formation Stirring and Solution Formation Stirring speeds up the dissolving process because fresh solvent (the water in tea) is continually brought into contact with the surface of the solute (sugar).

Temperature and Solution Formation 16.1 Solution Formation Temperature and Solution Formation At higher temperatures, the kinetic energy of water molecules is greater than at lower temperatures, so they move faster. As a result, the solvent molecules collide with the surface of the sugar crystals more frequently and with more force.

Particle Size and Solution Formation 16.1 Solution Formation Particle Size and Solution Formation A spoonful of granulated sugar dissolves more quickly than a sugar cube because the smaller particles in granulated sugar expose a much greater surface area to the colliding water molecules.

16.1 Solubility Solubility How is solubility usually expressed?

16.1 Solubility A saturated solution contains the maximum amount of solute for a given quantity of solvent at a given temperature and pressure. An unsaturated solution contains less solute than a saturated solution at a given temperature and pressure.

16.1 Solubility In a saturated solution, the rate of dissolving equals the rate of crystallization, so the total amount of dissolved solute remains constant. In a saturated solution, a state of dynamic equilibrium exists between the solution and the excess solute. The rate of solvation (dissolving) equals the rate of crystallization, so the total amount of dissolved solute remains constant. Inferring What would happen if you added more solute?

Solubility is often expressed in grams of solute per 100 g of solvent. 16.1 Solubility The solubility of a substance is the amount of solute that dissolves in a given quantity of a solvent at a specified temperature and pressure to produce a saturated solution. Solubility is often expressed in grams of solute per 100 g of solvent.

Two liquids are immiscible if they are insoluble in each other. 16.1 Solubility Some liquids combine in all proportions, while others don’t mix at all. Two liquids are miscible if they dissolve in each other in all proportions. Two liquids are immiscible if they are insoluble in each other.

Oil and water are immiscible. 16.1 Solubility Oil and water are immiscible. Liquids that are insoluble in one another are immiscible. a) A thin film of oil spreads over a water surface. Light rays, bent by the film, create patterns of color. b) Vinegar, which is water-based, and oil are immiscible.

Vinegar and oil are immiscible. 16.1 Solubility Vinegar and oil are immiscible. Liquids that are insoluble in one another are immiscible. a) A thin film of oil spreads over a water surface. Light rays, bent by the film, create patterns of color. b) Vinegar, which is water-based, and oil are immiscible.

Factors Affecting Solubility 16.1 Factors Affecting Solubility Factors Affecting Solubility What conditions determine the amount of solute that will dissolve in a given solvent?

Factors Affecting Solubility 16.1 Factors Affecting Solubility Temperature affects the solubility of solid, liquid, and gaseous solutes in a solvent; both temperature and pressure affect the solubility of gaseous solutes.

Factors Affecting Solubility 16.1 Factors Affecting Solubility Temperature The solubility of most solid substances increases as the temperature of the solvent increases. The solubilities of most gases are greater in cold water than in hot.

Factors Affecting Solubility 16.1 Factors Affecting Solubility The mineral deposits around hot springs result from the cooling of the hot, saturated solution of minerals emerging from the spring. Mineral deposits form around the edges of this hot spring because the hot water is saturated with minerals. As the water cools, some of the minerals crystallize because they are less soluble at the lower temperature.

Factors Affecting Solubility 16.1 Factors Affecting Solubility Changing the temperature usually affects the solubility of a substance. INTERPRETING GRAPHS a. Describe What happens to the solubility of KNO3 as the temperature increases? b. Identify Which substance shows a decrease in solubility as temperature increases? Which substance exhibits the least change in solubility? c. Apply Concepts Suppose you added some solid sodium chloride (NaCl) to a saturated solution of sodium chloride at 20°C and warmed the mixture to 40°C. What would happen to the added sodium chloride?

Factors Affecting Solubility 16.1 Factors Affecting Solubility A supersaturated solution contains more solute than it can theoretically hold at a given temperature. The crystallization of a supersaturated solution can be initiated if a very small crystal, called a seed crystal, of the solute is added.

Factors Affecting Solubility 16.1 Factors Affecting Solubility A supersaturated solution is clear before a seed crystal is added. A supersaturated solution crystallizes rapidly when disturbed. a) The solution is clear before a seed crystal is added. b) Crystals begin to form in the solution immediately after the addition of a seed crystal. c) Excess solute crystallizes rapidly. Applying Concepts When the crystallization has ceased, will the solution be saturated or unsaturated?

Factors Affecting Solubility 16.1 Factors Affecting Solubility Crystals begin to form in the solution immediately after the addition of a seed crystal. A supersaturated solution crystallizes rapidly when disturbed. a) The solution is clear before a seed crystal is added. b) Crystals begin to form in the solution immediately after the addition of a seed crystal. c) Excess solute crystallizes rapidly. Applying Concepts When the crystallization has ceased, will the solution be saturated or unsaturated?

Factors Affecting Solubility 16.1 Factors Affecting Solubility Excess solute crystallizes rapidly. A supersaturated solution crystallizes rapidly when disturbed. a) The solution is clear before a seed crystal is added. b) Crystals begin to form in the solution immediately after the addition of a seed crystal. c) Excess solute crystallizes rapidly. Applying Concepts When the crystallization has ceased, will the solution be saturated or unsaturated?

Factors Affecting Solubility Simulation 20 Observe the effect of temperature on the solubility of solids and gases in water.

Factors Affecting Solubility 16.1 Factors Affecting Solubility

Factors Affecting Solubility 16.1 Factors Affecting Solubility Pressure Changes in pressure have little effect on the solubility of solids and liquids, but pressure strongly influences the solubility of gases. Gas solubility increases as the partial pressure of the gas above the solution increases.

Factors Affecting Solubility 16.1 Factors Affecting Solubility Henry’s law states that at a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P) of the gas above the liquid. Pressure is a factor in the solubility of a gas. a) In a sealed bottle, both the pressure of CO2 above the liquid and the concentration of CO2 in the liquid are high and equal. b) When the cap is removed, the equilibrium is disturbed; the pressure of CO2 gas above the liquid decreases and carbon dioxide bubbles out of the liquid.

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for Sample Problem 16.1 Problem Solving 16.2 Solve Problem 2 with the help of an interactive guided tutorial.

16.1 Section Quiz. 16.1.

16.1 Section Quiz. 1. For a given substance, which of the following will NOT influence how fast it dissolves? temperature amount of agitation molar mass size of the crystals

16.1 Section Quiz. 2. The solubility of a substance is often expressed as the number of grams of solute per 100 liters of solvent. 1 cm3 of solvent. 100 grams of solution. 100 grams of solvent.

16.1 Section Quiz. 3. The solubility of a gas in a solvent is affected by both temperature and pressure. only pressure. only temperature. both pressure and agitation.

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Chemistry 16.2 Chapter 16 Section 2

Concentrations of Solutions 16.2 Water must be tested continually to ensure that the concentrations of contaminants do not exceed established limits. These contaminants include metals, pesticides, bacteria, and even the by-products of water treatment. You will learn how solution concentrations are calculated.

Molarity How do you calculate the molarity of a solution? 16.2

She then transfers the 20 mL to a 100-mL volumetric flask. 16.2 Making Dilutions She then transfers the 20 mL to a 100-mL volumetric flask. The student is preparing 100 mL of 0.40M MgSO4 from a stock solution of 2.0M MgSO4 . a) She measures 20 mL of the stock solution with a 20-mL pipet. b) She transfers the 20 mL to a 100-mL volumetric flask. c) She carefully adds water to the mark to make 100 mL of solution. Inferring How many significant figures does the new molarity have?

16.2 Making Dilutions Finally she carefully adds water to the mark to make 100 mL of solution. The student is preparing 100 mL of 0.40M MgSO4 from a stock solution of 2.0M MgSO4 . a) She measures 20 mL of the stock solution with a 20-mL pipet. b) She transfers the 20 mL to a 100-mL volumetric flask. c) She carefully adds water to the mark to make 100 mL of solution. Inferring How many significant figures does the new molarity have?

Volume-Measuring Devices 16.2 Making Dilutions Volume-Measuring Devices The photo shows a buret, a graduated cylinder, a volumetric flask, and a volumetric pipet. These are just some examples of volume-measuring devices.

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for Sample Problem 16.4 ` Problem Solving 16.12 Solve Problem 12 with the help of an interactive guided tutorial.

16.2 Percent Solutions Percent Solutions What are two ways to express the percent concentration of a solution?

16.2 Percent Solutions The concentration of a solution in percent can be expressed in two ways: as the ratio of the volume of the solute to the volume of the solution or as the ratio of the mass of the solute to the mass of the solution.

Concentration in Percent (Volume/Volume) 16.2 Percent Solutions Concentration in Percent (Volume/Volume)

16.2 Percent Solutions Isopropyl alcohol (2-propanol) is sold as a 91% solution. This solution consist of 91 mL of isopropyl alcohol mixed with enough water to make 100 mL of solution. The label clearly distinguishes this solution of isopropyl alcohol from rubbing alcohol, which is a 70% solution of isopropyl alcohol. Applying Concepts How many milliliters of isopropyl alcohol are in 100 mL of 91% alcohol?

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Concentration in Percent (Mass/Mass) 16.2 Percent Solutions Concentration in Percent (Mass/Mass)

16.2 Section Quiz. 1. To make a 1.00M aqueous solution of NaCl, 58.4 g of NaCl are dissolved in 1.00 liter of water. enough water to make 1.00 liter of solution 1.00 kg of water. 100 mL of water.

16.2 Section Quiz. 2. What mass of sodium iodide (NaI) is contained in 250 mL of a 0.500M solution? 150 g 75.0 g 18.7 g 0.50 g

16.2 Section Quiz. 3. Diluting a solution does NOT change which of the following? concentration volume milliliters of solvent moles of solute

16.2 Section Quiz. 4. In a 2000 g solution of glucose that is labeled 5.0% (m/m), the mass of water is 2000 g. 100 g. 1995 g. 1900 g.

END OF Section 2

Chemistry 16.3 Chapter 16 Section 3

Colligative Properties of Solutions 16.3 The wood frog is a remarkable creature because it can survive being frozen. Scientists believe that a substance in the cells of this frog acts as a natural antifreeze, which prevents the cells from freezing. You will discover how a solute can change the freezing point of a solution.

Vapor-Pressure Lowering 16.3 Vapor-Pressure Lowering Vapor-Pressure Lowering What are three colligative properties of solutions?

Vapor-Pressure Lowering 16.3 Vapor-Pressure Lowering A property that depends only upon the number of solute particles, and not upon their identity, is called a colligative property.

Vapor-Pressure Lowering 16.3 Vapor-Pressure Lowering Three important colligative properties of solutions are vapor-pressure lowering boiling-point elevation freezing-point depression

Vapor-Pressure Lowering 16.3 Vapor-Pressure Lowering In a pure solvent, equilibrium is established between the liquid and the vapor. The vapor pressure of a solution of a nonvolatile solute is less than the vapor pressure of a pure solvent. a) In a pure solvent, equilibrium is established between the liquid and the vapor. b) In a solution, solute particles reduce the number of free solvent particles able to escape the liquid. Equilibrium is established at a lower vapor pressure. Interpreting Diagrams How is decreased vapor pressure represented in the diagram?

Vapor-Pressure Lowering 16.3 Vapor-Pressure Lowering In a solution, solute particles reduce the number of free solvent particles able to escape the liquid. Equilibrium is established at a lower vapor pressure. The vapor pressure of a solution of a nonvolatile solute is less than the vapor pressure of a pure solvent. a) In a pure solvent, equilibrium is established between the liquid and the vapor. b) In a solution, solute particles reduce the number of free solvent particles able to escape the liquid. Equilibrium is established at a lower vapor pressure. Interpreting Diagrams How is decreased vapor pressure represented in the diagram?

Vapor-Pressure Lowering 16.3 Vapor-Pressure Lowering The decrease in a solution’s vapor pressure is proportional to the number of particles the solute makes in solution.

Vapor-Pressure Lowering 16.3 Vapor-Pressure Lowering Three moles of glucose dissolved in water produce 3 mol of particles because glucose does not dissociate. Particle concentrations differ for dissolved covalent and ionic compounds in water. a) Three moles of glucose dissolved in water produce 3 mol of particles because glucose does not dissociate. b) Three moles of sodium chloride dissolved in water produce 6 mol of particles because each formula unit of NaCl dissociates into two ions. c) Three moles of calcium chloride dissolved in water produce 9 mol of particles because each formula unit of CaCl2 dissociates into three ions.

Vapor-Pressure Lowering 16.3 Vapor-Pressure Lowering Three moles of sodium chloride dissolved in water produce 6 mol of particles because each formula unit of NaCl dissociates into two ions. Particle concentrations differ for dissolved covalent and ionic compounds in water. a) Three moles of glucose dissolved in water produce 3 mol of particles because glucose does not dissociate. b) Three moles of sodium chloride dissolved in water produce 6 mol of particles because each formula unit of NaCl dissociates into two ions. c) Three moles of calcium chloride dissolved in water produce 9 mol of particles because each formula unit of CaCl2 dissociates into three ions.

Vapor-Pressure Lowering 16.3 Vapor-Pressure Lowering Three moles of calcium chloride dissolved in water produce 9 mol of particles because each formula unit of CaCl2 dissociates into three ions. Particle concentrations differ for dissolved covalent and ionic compounds in water. a) Three moles of glucose dissolved in water produce 3 mol of particles because glucose does not dissociate. b) Three moles of sodium chloride dissolved in water produce 6 mol of particles because each formula unit of NaCl dissociates into two ions. c) Three moles of calcium chloride dissolved in water produce 9 mol of particles because each formula unit of CaCl2 dissociates into three ions.

Freezing-Point Depression 16.3 Freezing-Point Depression Freezing-Point Depression What factor determines the amount by which a solution’s vapor pressure, freezing point, and boiling point differ from those properties of the solvent?

Freezing-Point Depression 16.3 Freezing-Point Depression The difference in temperature between the freezing point of a solution and the freezing point of the pure solvent is the freezing-point depression.

Freezing-Point Depression 16.3 Freezing-Point Depression The magnitude of the freezing-point depression is proportional to the number of solute particles dissolved in the solvent and does not depend upon their identity.

Freezing-Point Depression 16.3 Freezing-Point Depression The freezing-point depression of aqueous solutions makes walks and driveways safer when people sprinkle salt on icy surfaces to make ice melt. The melted ice forms a solution with a lower freezing point than that of pure water. Surfaces can be free of ice even at temperatures below freezing if salt is applied. Inferring Why would calcium chloride (CaCl2) be a better salt for this purpose than sodium chloride (NaCl)?

Boiling-Point Elevation 16.3 Boiling-Point Elevation Boiling-Point Elevation The difference in temperature between the boiling point of a solution and the boiling point of the pure solvent is the boiling-point elevation. The same antifreeze added to automobile engines to prevent freeze-ups in winter, protects the engine from boiling over in summer.

Boiling-Point Elevation 16.3 Boiling-Point Elevation The magnitude of the boiling-point elevation is proportional to the number of solute particles dissolved in the solvent. The boiling point of water increases by 0.512°C for every mole of particles that the solute forms when dissolved in 1000 g of water.

16.3 Section Quiz. 16.3.

16.3 Section Quiz. 2. Choose the correct word for the space: The magnitude of each colligative property of solutions is proportional to the __________ solute dissolved in the solution. type of number of particles of molar volume of particle size of the

16.3 Section Quiz. 2. Choose the correct word for the space: The magnitude of each colligative property of solutions is proportional to the __________ solute dissolved in the solution. type of number of particles of molar volume of particle size of the

16.3 Section Quiz. 3. The decrease in vapor pressure when a solute is added to a liquid is due to attractive forces between solvent particles. repulsion of the solute particles by the solvent particles. dissociation of the solvent particles. attractive forces between solvent and solute particles.

16.3 Section Quiz. 4. You have 500 mL of 1M solutions of NaCl, Na2SO4, Na3PO4, and Al2(SO4)3. Which solution will have the highest boiling point? NaCl(aq) Na2SO4(aq) Na3PO4(aq) Al2(SO4)3(aq)

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Chemistry 16.4

Calculations Involving Colligative Properties 16.4 Cooking instructions often call for the addition of a small amount of salt to the cooking water. Dissolved salt elevates the boiling point of water. You will learn how to calculate the amount the boiling point of the cooking water rises.

Molality and Mole Fraction 16.4 Molality and Mole Fraction Molality and Mole Fraction What are two ways of expressing the concentration of a solution?

Molality and Mole Fraction 16.4 Molality and Mole Fraction The unit molality and mole fractions are two additional ways in which chemists express the concentration of a solution.

Molality and Mole Fraction 16.4 Molality and Mole Fraction The unit molality and mole fractions are two additional ways in which chemists express the concentration of a solution.

Molality and Mole Fraction 16.4 Molality and Mole Fraction The unit molality (m) is the number of moles of solute dissolved in 1 kilogram (1000 g) of solvent. Molality is also known as molal concentration.

Molality and Mole Fraction 16.4 Molality and Mole Fraction To make a 0.500m solution of NaCl, use a balance to measure 1.000 kg of water and add 0.500 mol (29.3 g) of NaCl. To make a 0.500m solution of NaCl, use a balance to measure 1.000 kg of water and add 0.500 mol (29.3 g) NaCl. Calculating What would be the molality if only 0.500 kg of water were used?

Molality and Mole Fraction 16.4 Molality and Mole Fraction Ethlylene Glycol (EG) is added to water as antifreeze. Ethylene glycol (EG) is added to water as antifreeze in the proportions shown. A mole fraction is the ratio of the number of moles of one substance to the total number of moles of all substances in the solution. Inferring What is the sum of all mole fractions in a solution?

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Practice ProblemsFor Sample Problem 16.6 Problem Solving 16.29 Solve Problem 29 with the help of an interactive guided tutorial.

Molality and Mole Fraction 16.4 Molality and Mole Fraction The mole fraction of a solute in a solution is the ratio of the moles of that solute to the total number of moles of solvent and solute.

Molality and Mole Fraction 16.4 Molality and Mole Fraction In a solution containing nA mol of solute A and nB mol of solvent B (XB), the mole fraction of solute A (XA) and the mole fraction of solvent B (XB) can be expressed as follows.

16.7 The concentration of antifreeze used in an automobile cooling system can be described by mole fractions.

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16.7 Sample Problem 16.7

for Practice Problem 16.7 Problem Solving 16.32 Solve Problem 32 with the help of an interactive guided tutorial.

Freezing-Point Depression and Boiling-Point Elevation 16.4 Freezing-Point Depression and Boiling-Point Elevation Freezing-Point Depression and Boiling- Point Elevation How are freezing-point depression and boiling-point elevation related to molality?

Freezing-Point Depression and Boiling-Point Elevation 16.4 Freezing-Point Depression and Boiling-Point Elevation The magnitudes of the freezing-point depression and the boiling-point elevation of a solution are directly proportional to the molal concentration (m), when the solute is molecular, not ionic.

Freezing-Point Depression and Boiling-Point Elevation 16.4 Freezing-Point Depression and Boiling-Point Elevation The constant, Kf, is the molal freezing-point depression constant, which is equal to the change in freezing point for a 1-molal solution of a nonvolatile molecular solute.

Freezing-Point Depression and Boiling-Point Elevation 16.4 Freezing-Point Depression and Boiling-Point Elevation

Freezing-Point Depression and Boiling-Point Elevation 16.4 Freezing-Point Depression and Boiling-Point Elevation The constant, Kb, is the molal boiling-point elevation constant, which is equal to the change in boiling point for a 1-molal solution of a nonvolatile molecular solute.

Freezing-Point Depression and Boiling-Point Elevation 16.4 Freezing-Point Depression and Boiling-Point Elevation

Freezing-Point Depression and Boiling-Point Elevation Simulation 21 Discover the principle underlying the colligative properties of solutions.

Freezing-Point Depression and Boiling-Point Elevation 16.4 Freezing-Point Depression and Boiling-Point Elevation The graph shows the relationship between vapor pressure and temperature for pure water and aqueous solutions. INTERPRETING GRAPHS a. Identify What is the freezing point of water? What is the boiling point? b. Describe How do the freezing and boiling points of the solution compare to those of pure water? c. Apply Concepts Does adding a solute to water allow it to remain as a liquid over a longer or shorter temperature range? Explain.

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for Sample Problem 16.8 Problem Solving 16.33 Solve Problem 33 with the help of an interactive guided tutorial.

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for Sample Problem 16.9 Problem Solving 16.36 Solve Problem 36 with the help of an interactive guided tutorial.

16.4 Section Quiz. 1. What is the mole fraction of He in a gaseous solution containing 4.0 g of He, 6.5 g of Ar, and 10.0 g of Ne? 0.60 1.5 0.20 0.11

16.4 Section Quiz. 2. The freezing point depression caused by a given concentration of a nonvolatile molecular solute depends on the solute. depends on the solvent. is always the same. cannot be determined.

16.4 Section Quiz. 3. What are the freezing and boiling points of a 0.1m solution of CaCl2 in water? -0.2°C, 100.1°C -0.6°C, 100.1°C -0.6°C, 100.2°C -0.6°C, 99.8°C

16.4 Section Quiz. 4. Compared to the freezing point depression by ethylene glycol (C2H6O2,) for a given solvent, the freezing point depression caused by the same molal concentration of CaCl2 would be exactly the same. twice as large. three times as large. four times as large

END OF Chapter 16