CHAPTER 14 Solutions
Classification of Matter Solutions are homogeneous mixtures
Solute A solute is the dissolved substance in a solution. Salt in salt water Sugar in soda drinks Carbon dioxide in soda drinks Solvent A solvent is the dissolving medium in a solution. Water in salt water Water in soda
Suspensions and Colloids Suspensions and colloids are NOT solutions. Suspensions: The particles are so large that they settle out of the solvent if not constantly stirred. Colloids: The particles intermediate in size between those of a suspension and those of a solution.
Tyndall Effect Many colloids appear homogeneous because the individual particles cannot be seen. The particles are, however, large enough to scatter light. You have probably noticed that a headlight beam is visible on a foggy night. This effect, known as the Tyndall effect, occurs when light is scattered by colloidal particles dispersed in a transparent medium. The Tyndall effect is a property that can be used to distinguish between a solution and a colloid
The Tyndall Effect Colloids scatter light, making a beam visible. Solutions do not scatter light. Which glass containsa colloid? colloid solution
Concentration of Solution OBJECTIVES Given the mass of solute and volume of solvent, calculate the concentration of a solution. Given the concentration of a solution, determine the amount of solute in a given amount of solution. Given the concentration of a solution, determine the amount of solution that contains a given amount of solute.
Concentration: of a solution is a measure of the amount of solute in a given amount of solvent or solution. • Example: some medications are solutions of drugs – a one teaspoon dose at the correct concentration might cure the patient, while the same dose in the wrong concentration might kill the patient.
Dilute: there is a small amount of solute in a solvent. Concentrated: there is a large amount of solute in the solvent
Molarity • Molarity: is the number of moles of solute in one liter of solution. (capital M)
One mole of NaOH has a mass of 40.0 g. If this quantity of NaOH is dissolved in enough water to make exactly 1.00 L of solution, the solution is a 1 M solution. • If 20.0 g of NaOH, which is 0.500 mol, is dissolved in enough water to make 1.00 L of solution, a 0.500 M NaOH solution is produced. • This relationship between molarity, moles, and volume may be expressed in the following ways.
Example • You have 3.50 L of solution that contains 90.0 g of sodium chloride, NaCl. What is the molarity of that solution? Grams of solute number of moles of solute molarity
Practice • You have 0.8 L of a .05 M HCl solution. How many moles of HCl does this solution contain? • What is the molarity of a solution composed of 5.85 g of Potassium iodide, KI, dissolved in enough water to make 0.125 L solution? • How many moles of H2SO4 are present in 0.500 L of a 0.150 M H2SO4 solution?
What is the molarity of a 2.5 L solution that is made from 15.3 g LiCl? • How many moles are present in 0.350 L of a 3.20 M solution?
Molality • Is the concentration of a solution expressed in moles of solute per kilogram of solvent.
One mole of NaOH has a molar mass of 40.0 g, so 40.0 g of NaOH dissolved in 1 kg of water results in a one-molal NaOH solution. • If 20.0 g of NaOH, which is 0.500 mol of NaOH, is dissolved in exactly 1 kg of water, the concentration of the solution is 0.500 m NaOH.
Example • A solution was prepared by dissolving 17.1 g sucrose (table sugar C12H22O11) in 125 g of water. Find the molal concentration of this solution.
To find molality, you need moles of solute and kilograms of solvent. The given grams of sucrose must be converted to moles.The mass in grams of solvent must be converted to kilograms.
Practice • What is the molality of a solution composed of 225 g of acetone,(CH3)2CO, dissolved in 200. g of water?
Practice2 • What is the molaRity of a solution composed of 225 g of acetone,(CH3)2CO, dissolved in 200. g of water?
What quantity, in grams, of methanol, CH3OH, is required to prepare a 0.244 m solution on 400 g of water?
Dilution of molar solutions Important Notes • M1V1=M2V2 • M is molarity; V is volume
Solute-Solvent Interations • LiCl dissolves in water, but not gasoline • Gasoline dissolves in benzene, but LiCl does not. • Why the difference??????
Homework • Packet pg 2-6 • Text page 483 (16-18) • 484 (20-23) • 485 (16-18)
Ch 14.3 Solution concentrations Turn in your homework Turn in your labs
14.3 Factors that Affect the Rate of Dissolution • Increased surface area of Solute • Agitating solution • Heating the solvent
Solvation • Molecular Solvation • molecules stay intact C6H12O6(s) C6H12O6(aq)
Dissolution of sodium Chloride Dissociation = formation of ions from sulute
Definition of Electrolytes and Nonelectrolytes An electrolyte is: • A substance whose aqueous solution conducts • an electric current. A nonelectrolyte is: • A substance whose aqueous solution does not • conduct an electric current. Try to classify the following substances as electrolytes or nonelectrolytes…
Electrolytes? • Pure water • Tap water • Sugar solution • Sodium chloride solution • Hydrochloric acid solution • Lactic acid solution • Ethyl alcohol solution • Pure sodium chloride
Answers to Electrolytes ELECTROLYTES: NONELECTROLYTES: • Tap water (weak) • NaCl solution • HCl solution • Lactate solution (weak) • Pure water • Sugar solution • Ethanol solution • Pure NaCl But why do some compounds conduct electricity in solution while others do not…?
Review of Definitions • Solution - homogeneous mixture Solute - substance being dissolved Solvent - present in greater amount
UNSATURATED SOLUTION more solute dissolves SATURATED SOLUTION no more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form Solubility 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 solution
Solubility • A solution that contains the maximum amount of solute is saturated.ie full • A supersaturated solution contains more solute than a saturated solution under the same conditions. • A dynamic equilibrium solution exists between dissolution and crystallization of a substance dissolved in water.
Like Dissolves Like **Predicts whether one substance is soluble in another. • Depends on • Type of bonding • Polarity (or non-polarity of molecules) • Forces of attraction between solute and solvent
Ionic Compounds in aq solution (a polar solvent) • This is Ions (extreme polar) in water • Charged parts of the water separate the cations from the anions. • When referring to the solution process, water the solvent, is referred to by the term hydration.
Non-polar solvents • Ionic compounds not soluble in nonpolar solvents (no attraction of +/-) • Would LiCl dissolve in C6H5CH3? (nonpolar) Why? • Ionic compounds are not usually soluble in non-polar solvents.
Liquid Solute and Solvents • Liquid solutes and solvents that are not soluble in each other are described as being immiscible (ie toluene and water) Like dissolves Like • Miscible = liquids that dissolve in each other. • Examples are fats, oils, greases are all soluble in nonpolar liquids like CCl4, toluene and Gasoline