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Chapter16 Solutions

Chapter16 Solutions. 16.1 Properties of Solutions. Chemistry. Today we are learning to:- 1. Understand what is meant by solubility 2. Identify factors that affect solubility of a substance. Types of Solutions.

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Chapter16 Solutions

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  1. Chapter16 Solutions 16.1 Properties of Solutions

  2. Chemistry Today we are learning to:-1. Understand what is meant by solubility 2. Identify factors that affect solubility of a substance

  3. Types of Solutions • Solutions are a homogenous mixture of substances. Atoms, ions or molecules are spread out evenly throughout another substance. • All three states of matter form solutions for example a solid may be dissolved in another solid. Ex. Brass (zinc and copper alloy) • Usually we think of liquids as forming solution. Ex. Salt/water solution • Some vocabulary you must know: • Solute: the substance that dissolves. Ex salt. • Solvent: the substance that does the dissolving. Ex. water. • Solution: the solute dissolved in the solvent forms this. Ex. Salt solution. • Solubility: describes how easily a solute will dissolve in a solvent • Soluble: it dissolves • Insoluble: it doesn’t dissolve

  4. Types of Solutions • How do you know you have a solution? • Homogeneous mixture • Light passes straight through (not dispersed) • May be colored • Does not settle on standing • Doesn’t separate out when filtered

  5. Chapter 15&16 Solutions 16.1 Properties of Solutions

  6. Exothermic and Endothermic Processes 17.1 Factors Affecting Solubility • 1. The type of solvent and solute • Ionic solids and polar molecules will dissolve in polar solvents but not in non polar ones. Ex. in the ionic solid NaCl(s), Na+ ions are attracted to the negative pole of water molecules and Cl- ions to the positively charged pole of water molecules. • Nonpolar molecules will dissolve in nonpolar solvents but not in polar ones such as water Ex. Oils and fats are nonpolar. The will not dissolve in water (polar solvent) but will dissolve in gasoline (nonpolar solvent) • Like dissolves like

  7. Exothermic and Endothermic Processes 17.1

  8. Exothermic and Endothermic Processes 17.1 Factors Affecting Solubility • 2. Temperature • Usually as temperature increases substances become more soluble in water. • Exceptions to this rule include gases, which come out of solution as temperature increases.

  9. Exothermic and Endothermic Processes 17.1 Factors Affecting Solubility • 3. Pressure • Usually has no effect on solubility of solids or liquids. • Solubility of gases increases as pressure increases. • Ex. Soda water has a lot of carbon dioxide gas dissolved in it as it is under high pressure. When a can is opened the pressure in the can drops and the carbon dioxide escapes as bubbles • Now try review questions 1-12 on page 120 and 121

  10. Exothermic and Endothermic Processes 17.1 Solubility Graphs • 1. The type of solvent and solute • Ionic solids and polar molecules will dissolve in polar solvents but not in non polar ones. Ex. in the ionic solid NaCl(s), Na+ ions are attracted to the negative pole of water molecules and Cl- ions to the positively charged pole of water molecules. • Nonpolar molecules will dissolve in nonpolar solvents but not in polar ones such as water Ex. Oils and fats are nonpolar. The will not dissolve in water (polar solvent) but will dissolve in gasoline (nonpolar solvent) • Like dissolves like

  11. gases solids Exothermic and Endothermic Processes 17.1 Solubility Graphs (Table G) Solubility vs. Temperature for Solids 140 KI • Shows number of grams of substance that can be dissolved in 100g of water at a given temperature. • The line shows the maximum amount of that substance that can dissolve at that temperature. 130 120 NaNO3 110 100 KNO3 90 80 HCl NH4Cl • Look at the solubility curve for potassium nitrate only 70 Solubility (grams of solute/100 g H2O) 60 NH3 KCl 50 40 30 NaCl KClO3 20 10 SO2 0 10 20 30 40 50 60 70 80 90 100

  12. Exothermic and Endothermic Processes 17.1 Solubility Graphs (Table G) Solubility vs. Temperature for Solids 140 130 Where the temperature is 40C 120 110 Above the curve the solution is supersaturated. The solution is unstable. Addition of a single crystal will cause rapid crystalization 100 KNO3 90 80 70 Solubility (grams of solute/100 g H2O) 60 On the curve the solution is saturated. This means we are at the maximum mass of KNO3 that will dissolve at that temperature 50 40 30 20 Below the curve the solution is unsaturated. This means we could dissolve more KNO3 10 0 10 20 30 40 50 60 70 80 90 100

  13. Exothermic and Endothermic Processes 17.1 Solubility Graphs (Table G) Solubility vs. Temperature for Solids 140 130 Where the mass of KNO3 is 60 g/100g H2O 120 110 The solution is supersaturated. The solution is unstable. Addition of a single crystal will cause rapid crystalization 100 KNO3 90 80 70 Solubility (grams of solute/100 g H2O) 60 On the curve the solution is saturated. This means we are at the maximum mass of KNO3 that will dissolve at that temperature 50 40 30 20 Unsaturated solution cools 10 0 10 20 30 40 50 60 70 80 90 100

  14. Ex1: What substance has a solubility of 73 g/100 cm3 of water at a temperature of 90ºC ? NH4Cl (ammonium chloride) Ex2: At what temperature will potassium nitrate have a solubility of 95 g/100 cm3 ? 55ºC Ex3: 30 grams of potassium nitrate has been added to 100 cm3 of water at a temperature of 50ºC. How many additional grams of solute must be added in order to make it saturated?

  15. From graph you can see that the solubility for potassium nitrate at 50ºC is 84 grams So we need to add 84-30 = 54g of potassium nitrate. Ex3: 30 grams of potassium nitrate has been added to 100 cm3 of water at a temperature of 50ºC. How many additional grams of solute must be added in order to make it saturated?

  16. Exothermic and Endothermic Processes 17.1 • Now try review questions 13-23 on page 123

  17. END OF SHOW

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