Chemistry Mrs. Nunez Solution - Solution - homogeneous mixture Solvent Solvent - present in greater amount Solute Solute - substance being dissolved Solvation the process of dissolving solute particles are separated and pulled into solution solute particles are surrounded by solvent particles Strong Electrolyte Non- Electrolyte solute exists as ions only - + salt - + sugar solute exists as molecules only - + acetic acid Weak Electrolyte solute exists as ions and molecules DISSOCIATIONIONIZATION Dissociation separation of an ionic solid into aqueous ions NaCl(s) Na + (aq) + Cl (aq) Ionization breaking apart of some polar molecules into aqueous ions HNO 3 (aq) + H 2 O(l) H 3 O + (aq) + NO 3 (aq) Molecular Solvation molecules stay intact C 6 H 12 O 6 (s) C 6 H 12 O 6 (aq) NONPOLAR POLAR Like Dissolves Like Like Dissolves Like C. Johannesson Soap/Detergent Soap/Detergent polar head with long nonpolar tail dissolves nonpolar grease in polar water Solubility SATURATED SOLUTION no more solute dissolves UNSATURATED SOLUTION more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form concentration Solubility maximum grams of solute that will dissolve in 100 g of solvent at a given temperature varies with temp based on a saturated soln Factors determining rate of solution stirring (agitation) 2. surface area the dissolving particles 3. temperature C. Johannesson C. Solubility Solids are more soluble at... Solids are more soluble at... high temperatures. Gases are more soluble at... low temperatures & high pressures (Henrys Law). EX: nitrogen narcosis, the bends, soda Solubility Solubility Curve Solubility Curve shows the dependence of solubility on temperature Solids tend to dissolve best when: They are heated They are stirred Crushed into smaller particles Gases tend to dissolve best when: The solution is cold The pressure is high Liquids Miscible means that two liquids can dissolve in each other water and antifreeze water and ethanol Partially miscible- slightly water and ether Immiscible means they cant oil and vinegar Gases in liquids... Henrys Law - says the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid think of a bottle of soda pop, removing the lid releases pressure Equation: S 1 S 2 P 1 P 2 Sample 16.1, page 477 = Concentration The amount of solute in a solution. Describing Concentration % by mass - medicated creams % by volume - rubbing alcohol ppm, ppb - water contaminants molarity - used by chemists molality - used by chemists Concentrated vs. Dilute Lots of solute, in a small amount of solvent. Small amount of solute in a large amount of solvent. Notice how dark the solutions appears. Notice how light the solution appears. CONCENTRATEDDILUTE A. Molarity Concentration of a solution. total combined volume substance being dissolved Molarity 2M HCl What does this mean? Molarity Calculations Find the molarity of a 250 mL solution containing 10.0 g of NaF g 1 mol g = mol NaF mol 0.25 L M == 0.95M NaF B. Molality mass of solvent only 1 kg water = 1 L water Molality Find the molality of a solution containing 75 g of MgCl 2 in 250 mL of water. 75 g MgCl 2 1 mol MgCl g MgCl 2 = 3.2 m MgCl kg water C. Dilution Preparation of a desired solution by adding water to a concentrate. Moles of solute remain the same. Dilution What volume of 15.8M HNO 3 is required to make 250 mL of a 6.0M solution? GIVEN: M 1 = 15.8M V 1 = ? M 2 = 6.0M V 2 = 250 mL WORK: M 1 V 1 = M 2 V 2 (15.8M) V 1 = (6.0M)(250mL) V 1 = 95 mL of 15.8M HNO 3 Preparing Solutions 500 mL of 1.54M NaCl 500 mL water 45.0 g NaCl mass 45.0 g of NaCl add water until total volume is 500 mL mass 45.0 g of NaCl add kg of water 500 mL mark 500 mL volumetric flask 1.54m NaCl in kg of water Preparing Solutions 250 mL of 6.0M HNO 3 by dilution measure 95 mL of 15.8M HNO 3 95 mL of 15.8M HNO 3 water for safet y 250 mL mark combine with water until total volume is 250 mL Safety: Do as you oughtta, add the acid to the watta! Percent solutions can be expressed by a) volume or b) mass Percent means parts per 100, so Percent by volume: = Volume of solute x 100% Volume of solution indicated %(v/v) Sample Problem 16.5, page 485 Percent solutions Another way to do mass percentage is as mass/mass: Percent by mass: = Mass of solute(g) x 100% Mass of solution (g) Indicated %(m/m) property that depends on the concentration of solute particles, not their identity Colligative Property Types Freezing Point Depression Freezing Point Depression ( t f ) f.p. of a solution is lower than f.p. of the pure solvent Boiling Point Elevation Boiling Point Elevation ( t b ) b.p. of a solution is higher than b.p. of the pure solvent Vapor pressure lowering Vapor pressure lowering - Page 488 Glucose will only have one particle in solution for each one particle it starts with. NaCl will have two particles in solution for each one particle it starts with. CaCl 2 will have three particles in solution for each one particle it starts with. Colligative Properties Some particles in solution will IONIZE (or split), while others may not. Freezing Point Depression Solute particles weaken IMF in the solvent. Boiling Point Elevation - Page 494 The addition of a solute would allow a LONGER temperature range, since freezing point is lowered and boiling point is elevated. Applications salting icy roads making ice cream antifreeze cars (-64C to 136C)