 # Solutions Homogeneous Mixtures - Solute & Solvent.

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Solutions Homogeneous Mixtures - Solute & Solvent

Objectives Identify various types of solutions Define solubility and the factors that affect it Correctly use the terms unsaturated, saturated and supersaturated Understand how to read a solubility graph Express concentration in terms of molarity Calculate the molarity of diluted solutions

Types of Solutions TypeExampleSolventSolute Gas Gas in GasAirN2N2 O2O2 Liquid Gas in LiquidCarbonated H 2 OH2OH2OCO 2 Liquid in LiquidVinegarH2OH2OAcetic Acid Solid in LiquidOcean WaterH2OH2ONaCl Solid Liquid in SolidDental AmalgamAgHg Solid in SolidSteelFeC

Solvent and Solute Solvent is the substance in the mixture in the greatest amount Solute is the substance in the mixture in the lesser amount

Solvation Process of surrounding solute particles with solvent particles Solvation of ionic compound produces electrolyte (ions in solution - can conduct electricity) Solvation of molecular compounds does not produce electrolyte

Which of the following would be a non- electrolyte? HCl (hydrochloric acid) NaOH (sodium hydroxide) CaCl 2 (calcium chloride) C 12 H 22 O 11 (sucrose)

Solubility Situation: you add more and more sugar to your iced tea - sugar crystals start to collect at bottom of glass Only a limited amount of solute can dissolve in a certain amount of solvent at a given set of conditions

Solubility Solubility = maximum amount of solvent that will dissolve in a given amount of solvent at a specific temperature and pressure

Factors that affect Solubility Temperature Pressure Agitation Breakage into small particles

Solubility Graph - Solids Most solids are more soluble as temperature of solution increases Greater kinetic energy of solvent helps surround solute particles

Solubility Graph - Gases Most gases are less soluble as temperature of solution increases Greater kinetic energy helps gases escape intermolecular forces attracting them to solvent particles

Question Given the following solubility curve for a particular solute in water, do you think the solute is a gas or a solid?

Saturated Solution Saturated solution contains the maximum amount of dissolved solute for given solvent amount at particular temperature and pressure Same rate of precipitation (solid coming out of solution) as dissolution (solid going into solution)

Unsaturated Solution Less than the maximum amount of solvent in a solution at particular temperature and pressure More solute can dissolve and stay in solution

Supersaturated Solution More than the maximum amount of solvent in a solution at particular temperature and pressure Can be made by dissolving solute in hot solvent and slowly cooling Slight disturbance will cause crystallization Watch video

Question You have a glass of water with salt dissolved in it. You add more salt, and it easily dissolves in the water. Is the solution unsaturated, saturated or supersaturated?

Concentration How much solute is dissolved in a solution Qualitative expression: dilute, concentrated Need quantitative way to express concentration

Expressing Concentration Various quantitative concentration ratios: percent by mass, percent by volume, mole fraction, molality, molarity We will focus on molarity - this is the most commonly used to express concentration of solute in liquid solution

Molarity Ratio of moles of solute to liters of solution Indicated by M.85 mol solute in 1 liter of solution = 0.85 M 0.85 M read as “0.85 molar” M = moles/liter

Question What is molarity of aqueous solution containing 40.0 g of glucose (C 6 H 12 O 6 ) in 1.5 liter of solution? First - convert grams of glucose into moles molar mass of glucose = 180 g/mol

Molarity Problem Continued 1mol/180 g (40 g) = 0.2 moles 0.2 mole/ 1.5 L = 0.133 M

Problems What is molarity of bleach solution containing 9.5 g of NaOCl per liter of bleach? Calculate the molarity of 1.60 L of a solution containing 1.55 g of dissolved KBr.

Preparing Molar Solutions You want to make a 1 L of a 1.5 molar solution of sucrose (C 12 H 22 O 11 - molar mass = 342 g/mol). How much sugar do you need? First - figure out how many grams of sucrose you need - 1.5 moles (342 g/mol) = 513 g Add 513 g of sucrose to volumetric flask. Add water until 1 liter mark reached. Amount of water will be less than 1 L. Why?

Diluting Solutions In labs, we use concentrated solutions of standard molarities called stock solutions For example, concentrated HCl is 12 M You want to have 1 liter of a 1.5 M solution of HCl - What do you do?

Preparing Dilutions M 1 V 1 = M 2 V 2 You want 1 L of 1.5 M HCl Figure out how much water you need to add: Solve for V 1 - this is how much concentrated solution you need V 1 = M 2 V 2 /M 1 V 1 = ((1.5 mol/L)(1 L))/(12 mol/L) V 1 = 0.125 L concentrated HCl - mix with DI water to dilute to 1 L

Questions - Write these down and work on them What volume, in mL of 2.00 M CaCl 2 stock solution would you use to make 0.50 L of 0.300M CaCl 2 solution? What volume of a 3.00 M KI stock solution would you use to make 0.300 L of a 1.25 M KI solution? How many mL of a 5.0 stock solution would you need to prepare 100 mL of 0.25 M H 2 SO 4 ? If you dilute 20.0 mL of a 3.5M solution to make 100 mL of solution, what is the molarity of the dilute solution?