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 Solutions are a homogenous mixture of substances. Atoms, ions or molecules are spread out evenly throughout another substance. i.All three states of matter form solutions for example a solid may be dissolved in another solid. Ex. Brass (zinc and copper alloy) ii.Usually we think of liquids as forming solution. Ex. Salt/water solution Solutions are a homogenous mixture of substances. Atoms, ions or molecules are spread out evenly throughout another substance. i.All three states of matter form solutions for example a solid may be dissolved in another solid. Ex. Brass (zinc and copper alloy) ii.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 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

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

Chapter 15&16 Solutions 16.1 Properties of Solutions

Exothermic and Endothermic Processes 17.1 Factors Affecting Solubility 1. The type of solvent and solute A.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. B.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) 1. The type of solvent and solute A.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. B.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

Exothermic and Endothermic Processes 17.1

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. 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.

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 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

Exothermic and Endothermic Processes 17.1 Solubility Graphs 1. The type of solvent and solute A.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. B.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) 1. The type of solvent and solute A.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. B.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

Exothermic and Endothermic Processes 17.1 Solubility Graphs (Table G) 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. 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 Solubility vs. Temperature for Solids Solubility (grams of solute/100 g H 2 O) KI KCl NaNO 3 KNO 3 HClNH 4 Cl NH 3 NaCl KClO 3 SO 2 gases solids Look at the solubility curve for potassium nitrate only

Exothermic and Endothermic Processes 17.1 Solubility Graphs (Table G) Solubility vs. Temperature for Solids Solubility (grams of solute/100 g H 2 O) KNO 3 Where the temperature is 40  C Below the curve the solution is unsaturated. This means we could dissolve more KNO 3 On the curve the solution is saturated. This means we are at the maximum mass of KNO 3 that will dissolve at that temperature Above the curve the solution is supersaturated. The solution is unstable. Addition of a single crystal will cause rapid crystalization

Exothermic and Endothermic Processes 17.1 Solubility Graphs (Table G) Solubility vs. Temperature for Solids Solubility (grams of solute/100 g H 2 O) KNO 3 Where the mass of KNO 3 is 60 g/100g H 2 O Unsaturated solution cools On the curve the solution is saturated. This means we are at the maximum mass of KNO 3 that will dissolve at that temperature The solution is supersaturated. The solution is unstable. Addition of a single crystal will cause rapid crystalization

Ex1: What substance has a solubility of 73 g/100 cm 3 of water at a temperature of 90ºC ? NH 4 Cl (ammonium chloride) Ex2: At what temperature will potassium nitrate have a solubility of 95 g/100 cm 3 ? 55ºC Ex3: 30 grams of potassium nitrate has been added to 100 cm 3 of water at a temperature of 50ºC. How many additional grams of solute must be added in order to make it saturated?

From graph you can see that the solubility for potassium nitrate at 50ºC is 84 grams So we need to add = 54g of potassium nitrate. Ex3: 30 grams of potassium nitrate has been added to 100 cm 3 of water at a temperature of 50ºC. How many additional grams of solute must be added in order to make it saturated?

Exothermic and Endothermic Processes 17.1 Now try review questions on page 123

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