Chapter 16 - Solutions Mr.Yeung Lesson 3 - Objectives • • • • • • Review Sweeeeet! Solubility Solubility curves Let’s solve some problems Concentrations Review • Polar and nonpolar • Endothermic and Exothermic reaction Solution definitions • Miscible – if the solution is same throughout or a homogenous mixture – Salt water – Or two liquids such as water and ethanol • Immiscible – if the solvent and solute cannot be blended together – Ex. Oil and water – Or two liquids oil and vinegar • Soluble • A solute is soluble if it dissolves in the solvent – Sugar in water • Insoluble • A solute is insoluble if it cannot dissolve in the solvent – Sand in water What happens when…? • I dissolve sugar into a beaker • How much sugar can I put in with 100ml of water? Types of solutions • Saturated solution – a solution that holds the maximum amount of solute possible at a given temperature • Unsaturated solution – a solution that holds the maximum amount of solute possible at a given temperature • Super-saturated solution – a solution that holds more than the maximum amount of solute possible at a given temperature How do you …? • Saturate a solution? – Add more solute – Evaporate the solvent • Why can’t you simply decrease the amount of solution? Super-saturated solution – a solution that holds more than the maximum amount of solute possible at a given temperature – Sugar crystals – Heat and dissolve sugar in water to more than it can hold (super saturating) – Slowly cool – Sugar will grow out of solution and crystallizes Solubility • What is 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 100g of solvent Solubility curves • Tell us what mass of solute will dissolve in 100g of water over a range of temperatures. • The lines indicate the concentration of a saturated solution - the maximum amount of solute that will dissolve at that specific temperature. • Values on the graph below a curve represent unsaturated solutions - more solute could be dissolved at that temperature. Values above a curve represent supersaturated solutions, a solution which holds more solute that can normally dissolve in that volume of solvent. Solubility curves Example of reading the curve • Here's an example of reading the chart. Find the curve for KClO3. • At 30°C approximately 10g of KClO3 will dissolve in 100g of water. If the temperature is increased to 80°C, approximately 40g of the substance will dissolve in 100g (or 100mL) of water. Questions – What mass of solute will dissolve in 100mL of water at the following temperatures? – 1.KNO3at 70°C ---130g/100ml – 2.NaCl at 100°C --- 40g/100ml – 3.NH4Cl at 90°C --- ~70g/100ml – Also determine which of the three substances is most soluble in water at 15°C. – NaCl Summary • Saturated, unsaturated, Supersaturated, • Solubility • Solubility curves • Concentrations