Ch. 8 Solutions, Acids, & Bases I. How Solutions Form Definitions Types of Solutions Dissolving Rate of Dissolving A. Definitions – a mixture that has the same composition throughout the mixture; a homogeneous mixture. Solution Solute - substance being dissolved (in lesser quantity) Solvent – what the solute is dissolved in (in greater quantity) A. Definitions Solute - KMnO4 Solvent - H2O Solutions – a mixture that has the same composition throughout the mix. Remember the difference between a mixture and a compound. • Compounds have a fixed composition throughout. • Mixtures can have a variable composition throughout. Solution A. Definitions – The maximum amount of solute that can be dissolved in the solvent at a given temperature. Solubility B. Types of Solutions solutions – maximum amount of solute at a given temperature. Saturated solutions – less than the maximum amount of solute at a given temperature. Unsaturated solutions – more than the maximum amount of solute at a given temperature; unstable. Supersaturated B. Types of Solutions UNSATURATED SOLUTION more solute dissolves SATURATED SOLUTION no more solute dissolves concentration SUPERSATURATED SOLUTION becomes unstable, crystals form C. Dissolving Solvation • occurs at the surface of the solute • solvent particles surround solute particles (+/- attraction) • solute particles are pulled into solution D. Rate of Dissolving Solids dissolve faster... • more stirring • small particle size (increased surface area) • high temperature Rate of Dissolving To increase rate of dissolving of SOLIDS: Heat it Crush Stir it it D. Rate of Dissolving Gases dissolve faster... • no shaking or stirring • high pressure • low temperature To make a gas dissolve more quickly in a liquid: • Cool it • Increase the pressure of the gas Ch. 8 Solutions, Acids, & Bases II. Concentration & Solubility A. Concentration % by Volume • usually liquid in liquid • Ex: 10% juice = 10mL juice + 90mL water % by Mass • usually solid in liquid • Ex: 20% NaCl = 20g NaCl + 80g water A. Concentration Concentrated solution • large amount of solute Dilute solution • small amount of solute B. Solubility Solubility • maximum grams of solute that will dissolve in 100 g of solvent at a given temperature • varies with temperature • based on a saturated solution B. Solubility Solids are more soluble at... • high temperatures Gases are more soluble at... • low temperatures • high pressures (Henry’s Law) C. Solubility Charts Reading Solubility Charts • If the number in the problem is EQUAL to the value on the chart the solution is considered SATURATED • If the number in the problem is LESS than the value on the chart the solution is considered UNSATURATED • If the number in the problem is MORE than the value on the chart the solution is considered SUPER SATURATED C. Solubility Charts Solubility of Compounds in g/100g of Water at various Temperatures Compound 0◦ C 20◦ C 60◦ C 100◦ C Ammonium chloride Copper(II) sulfate Lead(II)chloride Potassium bromide Sodium chlorate 29.4 23.1 0.67 53.6 79.6 37.2 32.0 1.0 65.3 95.9 55.3 61.8 1.94 85.5 137 77.3 114 3.2 104 204 Answer Questions on your paper Chart 1) How would you classify a solution of 65.3g of Saturated potassium bromide at 20ºC? _________ 2) How would you classify a solution of 65.3g of Unsaturated potassium bromide at 60ºC? ____________ 3) How would you classify a solution of 65.3g of Supersaturated potassium bromide at 0ºC? ______________ 4) How would you classify a solution of 37g of ammonium chloride at 20ºC? Unsaturated ___________ 5) How would you classify a solution of 2.5 g of Supersaturated lead (II) chloride at 20ºC? ______________ D. Solubility Graphs Solubility Curve • shows the dependence of solubility on temperature Graph 6) How would you classify a solution of 80g Supersaturated of HCl at 20ºC? ____________ 7) How would you classify a solution of 30g of KNO3 at 20ºC? Unsaturated __________ 8) How would you classify a solution of 39g Saturated of NaCl at 100ºC? ________ 9) How would you classify a solution of 80g Unsaturated of NaNO3 at 30ºC? __________ 10)How would you classify a solution of 40g of KClO3 at 80ºC? __________ Unsaturated 11)How many grams of solute would you need to form a saturated solution of NH4Cl 50 g at 50ºC? _____ 12)How would you classify a solution of 20g Unsaturated of SO2 at 0ºC? ___________ 13)How much KI would you need to form a 135 g saturated solution at 10ºC? _____ 14)Which solid decreases in solubility as the temperature increases? Na _______ 2SO4 Acid, Bases & Salt Video 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Pre Test True False True True False False True True False False 1. 2. 3. 4. 5. 6. 7. 8. 9. Post Test Neutralization Base Anion Electrolytes False False True False False 10. 11. 12. Post Test bitter, slippery, high pH Acids donate hydrogen, Bases accept Hydrogen An easy way to gauge is something is a strong/weak acid or base Ch. 8 Solutions, Acids, & Bases III. Particles in Solution “Like Dissolves Like” Electrolytes A. “Like Dissolves Like” Polar substances will only dissolve in polar liquids • Rubbing alcohol and water Nonpolar substances will only dissolve in nonpolar liquids • Oil and butter Substances that aren’t the same don’t mix. • Oil and water A. “Like Dissolves Like” NONPOLAR POLAR NONPOLAR Detergents • polar “head” with long nonpolar “tail” • can dissolve both types (polar and nonpolar) POLAR B. Electrolyte An electrolyte is a substance that when dissolved in water form ions Electrolytes get their name from the fact that the conduct electricity in water. Example: salt dissolved in water Many sports drinks contain “electrolytes” which are salts dissolved in water B. Electrolytes - + - salt Electrolyte solute exists as ions only Easily conducts electricity - + + acetic acid sugar Weak Electrolyte NonElectrolyte solute exists as ions and Molecules Slightly conducts electricity solute exists as molecules only Does NOT conduct electricity B. Electrolytes Dissociation • separation of +/ions when an ionic compound dissolves in water B. Electrolytes Ionization • breaking apart of polar covalent molecules into ions when dissolving in water Ch. 8 Solutions, Acids, & Bases IV. Intro to Acids & Bases Definitions Properties Uses A. Acids • Acids contain at least one hydrogen atom that can be removed when the acid is dissolved in water. • These form hydronium ions, H3O+. • Also called a proton donor HCl + H2O + H3O + – Cl A. Bases • Bases form hydroxide ions (OH-) in a water solution. • a proton acceptor NH3 + H2O + NH4 + OH A. Indicators • Indicators are an organic substance that changes color in an acid or base. Examples: • • • • litmus - red/blue phenolphthalein - colorless/pink goldenrod - yellow/red red cabbage juice - pink/green B. Properties sour pH taste less than 7 bitter pH taste greater than 7 corrosive corrosive electrolytes electrolytes turn turn litmus red litmus blue with metals to slippery feel form H gas react C. Uses –phosphoric acid - soft drinks, fertilizer, detergents H2SO4 – sulfuric acid - fertilizer, car batteries HCl – hydrochloric acid - gastric juice HC2H3O2 – acetic acid - vinegar H3PO4 C. Uses – sodium hydroxide -lye, drain and oven cleaner Mg(OH)2 – magnesium hydroxide laxative, antacid NH3 –ammonia - cleaners, fertilizer NaOH Ch. 8 Solutions, Acids, & Bases V. Strength of Acids & Bases Strength vs. Concentration Strong vs. Weak pH A. Strength vs. Concentration and weak – tells how easy the acid or base dissociates in solution. Concentration – The amount of acid or base in a solution. Strong It is possible to have a dilute concentration of a strong acid that would be less harmful than a concentrated weak acid. A. Strength of Acids & Bases The strength of an acid or base depends on how completely a compound separates into ions when dissolved in water. Ions can carry an electric charge so a strong acid will carry more electricity than weak acid. B. Strong vs. Weak Strong - + Weak - + Acid/Base • 100% ions in water • strong electrolyte • HCl, HNO3, NaOH, LiOH Acid/Base • few ions in water • weak electrolyte • HC2H3O2, NH3 B. Strong Acids Acids that ionize almost completely in a solution are strong acids. Ex: HCl, HNO3, and H2SO4 They have a very low pH (0-1). B. Strong Bases Bases that dissociate completely in a solution are strong bases. Ex: NaOH They have a very high pH (13-14) C. pH Scale pH (potential of Hydrogen) • a measure of the concentration of H+ ions in a solution • measured with a pH meter or an indicator with a wide color range (0-14) 14 0 7 INCREASING ACIDITY NEUTRAL INCREASING BASICITY C. pH Scale pH of Common Substances ConcepTest Which of the following "molecular" pictures best represents a concentrated solution of the weak acid HA? A B ConcepTest Is the following statement TRUE or FALSE? • A strong acid has a lower pH than a weak acid. • True• But: Strong/weak refers to amount of ionization whereas pH refers to concentration of H+. Ch. 8 Solutions, Acids, & Bases VI. Neutralization Neutralization Reaction A. Neutralization Reaction Chemical reaction between an acid and a base. Products are a salt (ionic compound) and water. A. Neutralization Reaction ACID + BASE SALT + WATER HCl + NaOH NaCl + H2O = Neutralization does not always mean pH = 7. A. Neutralization Reaction KOH + HNO3 H2O + KNO3 Acid HNO3 Base KOH Salt KNO3