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Unit 15Section 1 Homogenous and Heterogeneous Solutions

Section 2 Concentration of Solutions

Section 3 Properties of SolutionsSolutionsTo understand the process of dissolvingTo learn why certain substances dissolve in waterTo learn qualitative terms describing the concentration of a solution To understand the factors that affect the rate at which a solid dissolves Objectives Section 1 Homogenous and Heterogeneous SolutionsSolutions2A 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.

Solutions3What is a solution? Solution homogeneous mixture Solvent substance present in largest amount Solutes other substances in the solution Aqueous solution solution with water as the solvent Solutions4

Solutions5Solubility Ionic substances breakup into individual cations and anions. Solubility of Ionic Substances

Solutions6Solubility Polar water molecules interact with the positive and negative ions of a salt. Solubility of Ionic Substances

Solutions7Solubility Ethanol is soluble in water because of the polar OH bond. Solubility of Polar Substances

Solutions8Solubility Why is solid sugar soluble in water? Solubility of Polar Substances

Solutions9Solubility Nonpolar oil does not interact with polar water.Water-water hydrogen bonds keep the water from mixing with the nonpolar molecules. Substances Insoluble in Water

Solutions10Solubility A hole must be made in the water structure for each solute particle. The lost water-water interactions must be replaced by water-solute interactions. like dissolves like How Substances Dissolve Solutions11Solution Composition: An Introduction The solubility of a solute is limited. Saturated solution contains as much solute as will dissolve at that temperature Unsaturated solution has not reached the limit of solute that will dissolve Solutions12Solution Composition: An Introduction Supersaturated solution occurs when a solution is saturated at an elevated temperature and then allowed to cool but all of the solid remains dissolved Contains more dissolved solid than a saturated solution at that temperature Unstable adding a crystal causes precipitationSolutions13Solution Composition: An Introduction A supersaturated solution is clear before a seed crystal is added.

Solutions14A 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?

Solution Composition: An Introduction Crystals begin to form in the solution immediately after the addition of a seed crystal.

Solutions15A 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?

Solution Composition: An Introduction Excess solute crystallizes rapidly.

Solutions16A 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?

Solution Composition: An Introduction Solutions are mixtures.Amounts of substances can vary in different solutions. Specify the amounts of solvent and solutes Qualitative measures of concentrationconcentrated relatively large amount of solute dilute relatively small amount of solute Solutions17Solution Composition: An Introduction Which solution is more concentrated?

Solutions18Solution Composition: An Introduction Which solution is more concentrated?

Solutions19Factors Affecting the Rate of Dissolving Surface area Stirring Temperature Solutions20Factors Affecting the Rate of Dissolving A cube of sugar in cold tea dissolves slowly.

Solutions21Stirring 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.Factors Affecting the Rate of Dissolving Granulated sugar dissolves in cold water more quickly than a sugar cube, especially with stirring.

Solutions22Stirring 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.Factors Affecting the Rate of Dissolving Granulated sugar dissolves very quickly in hot tea.

Solutions23Stirring 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.

Factors Affecting the Rate of Dissolving Stirring and Solution FormationStirring speeds up the dissolving process because fresh solvent (the water in tea) is continually brought into contact with the surface of the solute (sugar).Solutions24Factors Affecting the Rate of Dissolving 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.Solutions25Factors Affecting the Rate of Dissolving Particle Size and Solution FormationA 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.Solutions26 To understand mass percent and how to calculate it To understand and use molarity To learn to calculate the concentration of a solution made by diluting a stock solution Objectives Section 2 Concentration of SolutionsSolutions27Solution Composition: Mass Percent

Solutions28Solution Composition: Molarity Concentration of a solution is the amount of solute in a given volume of solution.

Solutions29Solution Composition: Molarity Consider both the amount of solute and the volume to find concentration.

Solutions30Solution Composition: Molarity To find the moles of solute in a given volume of solution of known molarity use the definition of molarity.

Solutions31Solution Composition: Molarity Standard solution - a solution whose concentration is accurately known To make a standard solution Weigh out a sample of solute. Transfer to a volumetric flask. Add enough solvent to mark on flask.

Solutions32MolarityTo make a 0.5-molar (0.5M) solution, first add 0.5 mol of solute to a 1-L volumetric flask half filled with distilled water.

Solutions33The photos show how to make a 0.5-molar (0.5M) solution. a) Add 0.5 mol of solute to a 1-L volumetric flask half filled with distilled water. b) Swirl the flask carefully to dissolve the solute. c) Fill the flask with water exactly to the 1-L mark.MolaritySwirl the flask carefully to dissolve the solute.

Solutions34The photos show how to make a 0.5-molar (0.5M) solution. a) Add 0.5 mol of solute to a 1-L volumetric flask half filled with distilled water. b) Swirl the flask carefully to dissolve the solute. c) Fill the flask with water exactly to the 1-L mark.

MolarityFill the flask with water exactly to the 1-L mark.

Solutions35The photos show how to make a 0.5-molar (0.5M) solution. a) Add 0.5 mol of solute to a 1-L volumetric flask half filled with distilled water. b) Swirl the flask carefully to dissolve the solute. c) Fill the flask with water exactly to the 1-L mark.

Dilution Water can be added to an aqueous solution to dilute the solution to a lower concentration. Only water is added in the dilution the amount of solute is the same in both the original and final solution. Solutions36Dilution Diluting a solution Transfer a measured amount of original solution to a flask containing some water. Add water to the flask to the mark (with swirling) and mix by inverting the flask.

Solutions37Making DilutionsThe total number of moles of solute remains unchanged upon dilution, so you can write this equation.

M1 and V1 are the molarity and volume of the initial solution, and M2 and V2 are the molarity and volume of the diluted solution.

Solutions38Making DilutionsMaking a Dilute Solution

Solutions39Adding solvent to a concentrated solution lowers the concentration, but the total number of moles of solute present remains the same.

Making DilutionsTo prepare 100 ml of 0.40M MgSO4 from a stock solution of 2.0M MgSO4, a student first measures 20 mL of the stock solution with a 20-mL pipet.

Solutions40The 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?

Making DilutionsShe then transfers the 20 mL to a 100-mL volumetric flask.

Solutions41The 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?

Making DilutionsFinally she carefully adds water to the mark to make 100 mL of solution.

Solutions42The 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?

Making DilutionsVolume-Measuring Devices

Solutions43The photo shows a buret, a graduated cylinder, a volumetric flask, and a volumetric pipet. These are just some examples of volume-measuring devices.

To learn to solve stoichiometric problems involving solution reactions To do calculations involving acid-base reactionsTo learn about normality and equivalent weight To use normality in stoichiometric calculations To understand the effect of a solute on solution properties Objectives Section 3 Properties of SolutionsSolutions44Stoichiometry of Solution Reactions

Solutions45Neutralization Reactions An acid-base reaction is called a neutralization reaction. Steps to solve these problems are the same as before.

Solutions46Normality Unit of concentrationOne equivalent of acid amount of acid that furnishes 1 mol of H+ ions One equivalent of base amount of base that furnishes 1 mol of OH ions Equivalent weight mass in grams of 1 equivalent of acid or base Solutions47Normality

Solutions48Normality

Solutions49Normality To find number of equivalents

Solutions50Normality Advantage of equivalents

Solutions51Boiling Point and Freezing Point The presence of solute particles causes the liquid range to become wider. Boiling point increases Freezing point decreases Solutions52Boiling Point and Freezing Point Why does the boiling point of a solution increase? Solute particles block some of the water molecules trying to enter the bubble. Need higher pressure to maintain the bubble.

Forming a bubble in a solutionSolutions53Boiling Point and Freezing Point Comparing bubbles

Solutions54Boiling Point and Freezing Point Colligative property a solution property that depends on the number of solute particles present Solutions55