Chapter 12-13: Mixtures and Aqueous Solutions What are they? Where do we find them? How do we describe them? We use solutions all the time

Soluble versus insoluble Some solids are soluble in water, ie: table salt, NaCl. Soluble means: able to be dissolved. Some solids are soluble in water, ie: table salt, NaCl. Soluble means: able to be dissolved. Soluble ionic solids (made of cation and anion) dissociate into their ions in water. Soluble ionic solids (made of cation and anion) dissociate into their ions in water. Soluble covalent solids (like sugar) dissolve because they are relatively polar. Soluble covalent solids (like sugar) dissolve because they are relatively polar.

Back Bires, 2005 Slide 3 In a solution, the dissolved particles cannot be easily seen or separated from the solution. In a solution, the dissolved particles cannot be easily seen or separated from the solution. Alloys are solutions of metals! Alloys are solutions of metals!

Parts of a solution The dissolving medium is the solvent (what does the dissolving) The dissolving medium is the solvent (what does the dissolving) The dissolved substance is the solute (what gets dissolved) The dissolved substance is the solute (what gets dissolved) The solute and solvent together form the solution. The solute and solvent together form the solution. Solvents and solutes can be any phase. Solvents and solutes can be any phase. solution

Special types of mixtures - Suspensions Suspensions Suspensions –mixtures where the solutes particles are very large, so they don’t completely dissolve into their solvent. Solute particles will settle out of the solution if left undisturbed. – this creates two phases. Solute particles will settle out of the solution if left undisturbed. – this creates two phases. Muddy water and Italian salad dressing are good examples of suspensions. Muddy water and Italian salad dressing are good examples of suspensions.

Special types of mixtures - Colloids Colloids Colloids –mixtures where the solute particle is smaller than particles in a suspension, but not small enough to dissolve. Colloids have two phases: Colloids have two phases: Dispersed phase – the solute Dispersing medium – the solvent.

Back Bires, 2005 Slide 7Colloids Mayonnaise and hair gel are good examples of colloids. Mayonnaise and hair gel are good examples of colloids. There are 7 types of colloids, found on page 404… There are 7 types of colloids, found on page 404…

7 Types of Colloids Page 404 Two groups of colloids: Heterogeneous colloids – two phases are clearly seen Homogeneous colloids – appears to be one phase Colloid Type PhasesExample Sol solid in liquid, liquid substance Paint Gel solid in liquid, solid substance Gelatin Foam gas in liquid Whipped cream Liquid Emulsion liquid in liquid Milk, mayonnaise Solid Emulsion liquid in solid Cheese, butter Solid Aerosol solid in gas Smoke Liquid Aerosol liquid in gas Clouds, fog

The Tyndall Effect The Tyndall effect allows us to distinguish between solutions, colloids, and suspensions. It works by shining a beam of light into the mixture. If… John Tyndall, Brittish, c1860

Back Bires, 2005 Slide 10 Results of Tyndall Effect Light doesn’t pass through – –the mixture is a suspension or a heterogeneous colloid. Light passes through unobstructed – –the mixture is a solution. Light passes, but the beam can be seen in the mixture – –the mixture is a homogeneous colloid

Back Bires, 2005 Slide 11 The Tyndall Effect

Electrolytes Electrolytes Electrolytes –Solutions that conduct electricity. Ionic solutions are electrolytes. Ionic solutions are electrolytes. Covalent solutions are nonelectrolytes. Covalent solutions are nonelectrolytes.

Back Bires, 2005 Slide 13 What do you think? Is saltwater (NaCl in water) an electrolyte? Is sugar water (C 6 H 12 O 6 in water) an electrolyte? Conductivity tester (meter) –can tell us if a solution is an electrolyte, and sometimes, how strong an electrolyte is.

Back Bires, 2005 Slide 14 Warm Up- Would the following solutes be electrolytes or nonelectrolytes CaCl 2 CCl 4 SrBr 2 How do you know??

Back Bires, 2005 Slide 15 Warm Up Be sure you hand in any HW that you may not have had on test day… Article Analysis Review 12.2 Enthalpy WS 10.4 and 16.1 Notes

Solubility Solubility Solubility –The extent to which a solute will dissolve in a solvent. (how much solute will dissolve) High solubility High solubility –large amounts of solute will dissolve in a solvent Low solubility Low solubility –only small amounts of solute will dissolve

Back Bires, 2005 Slide 17Solubility Increasing temperature increases the solubility of solids in liquids. Increasing temperature increases the solubility of solids in liquids. Increasing temperature decreases the solubility of gases in liquids! … Increasing temperature decreases the solubility of gases in liquids! …

Back Bires, 2005 Slide 18 Reading Solubility Curves

Solid-Liquid solubility with temperature

Back Bires, 2005 Slide 20 Gas-Liquid solubility with temperature

Gases in liquids In addition to cold temperatures, high pressures increase solubility of gases in liquids. In addition to cold temperatures, high pressures increase solubility of gases in liquids. Henry’s Law: Henry’s Law: –solubility of a gas in a liquid increases with increasing pressure of that gas above the liquid.

Like Dissolves Like! Some solvents are polar, having partial negative and partial positive ends. (H 2 O) Some solvents are polar, having partial negative and partial positive ends. (H 2 O) Other solvents are nonpolar, having no “+” “-” poles Other solvents are nonpolar, having no “+” “-” poles Polar solutes tend to dissolve well in polar solvents… Polar solutes tend to dissolve well in polar solvents… Nonpolar solutes tend to dissolve well into nonpolar solvents. Nonpolar solutes tend to dissolve well into nonpolar solvents.

Back Bires, 2005 Slide 23 Like Dissolves Like Water is very polar. Does it dissolve polar substances or non polar substance?

Saturation Saturated Solution Saturated Solution –solution has as much solute in it as it will allow (equal to solubility) Unsaturated Solution Unsaturated Solution –more solute can still dissolve into solution (less than solubility) Supersaturated Solution Supersaturated Solution –too much solute in solution-some will fall out (more than solubility) We express the quantitative amount of solute in a solution with concentration … We express the quantitative amount of solute in a solution with concentration …

Solid-Liquid solubility with temperature

Back Bires, 2005 Slide 26 Solubility Graph Practice Work on the front side— 15 minutes Work on the back side- 15 minutes

Back Bires, 2005 Slide 27 KNO3 Lab

Back Bires, 2005 Slide 28 Warm Up

Concentration - Molarity The “Stoichiometry” of Solutions The “Stoichiometry” of Solutions Concentration Concentration –the quantitative amount of solute present in a solution Molarity (M) – moles/liter Molarity (M) – moles/liter –number of moles solute in liters of solution

Try these Molarity questions What is the concentration [in Molarity] when 3 moles of NaCl are dissolved in 2 Liters of water? What is the concentration [in Molarity] when 3 moles of NaCl are dissolved in 2 Liters of water? How much (in liters) of a 0.1 M solution do you need to get 2 moles of solute? How much (in liters) of a 0.1 M solution do you need to get 2 moles of solute? How many moles of NaOH are present in 300mL of a 1M solution? How many moles of NaOH are present in 300mL of a 1M solution? How many grams of HCl are found in 100mL of a 2M solution? How many grams of HCl are found in 100mL of a 2M solution? 1.5 M “molar” 20 L.3 moles 7.2 grams

Solution Preparation By solid dissolving: 1. Calculate how many grams are needed to create our volume of our desired molarity solution 2. Weigh out that mass, and add it to a volumetric flask 3. add some water and allow to dissolve 4. add water to the desired volume

Back Bires, 2005 Slide 32 Solution Preparation By dilution of a standard solution: 1. Use the relationship M 1 V 1 =M 2 V 2 2. Calculate volume of the “standard solution” to use to get desired volume of desired molarity solution.

Back Bires, 2005 Slide 33 Solution Formation The nature of the solvent and solute affects whether a substance will dissolve The nature of the solvent and solute affects whether a substance will dissolve Other factors determine how fast a soluble substance dissolves Other factors determine how fast a soluble substance dissolves –Agitation (shaking) –Temperature –Solute particle size

Will it dissolve? (Solubility Rules) Not all ionic solids (salts) will dissolve. Not all ionic solids (salts) will dissolve. We use solubility rules to decide if the substance will dissolve. We use solubility rules to decide if the substance will dissolve. Salts containing… Salts containing… 1. Alkali metal cations (+) are soluble. 2. NH 4 +, NO 3 -, SO 4 2- are soluble. 3. Pb +, Ag +, Hg 2+ are insoluble. 4. CO 3 -, PO 4 3-, S 2- are insoluble. Which of the following salts are soluble? Which of the following salts are soluble? NaCl, HgCO 3, Ca(NO 3 ) 2, AgF, PbI 2, FeSO 4 NaCl, HgCO 3, Ca(NO 3 ) 2, AgF, PbI 2, FeSO 4 BaSO4, SrSO4, and PbSO4 are insoluble

Dissociation and Ions Present Dissociation = a salt dissolving into its ions: Dissociation = a salt dissolving into its ions: How many moles of ions are in a solution of 1 mole of NaCl? How many moles of ions are in a solution of 1 mole of NaCl? How many moles of ions are in solutions of 1 mole of each of the following?: How many moles of ions are in solutions of 1 mole of each of the following?:

Net Ionic Equations When we write a balanced chemical equation, we show all species present (all reactants and all products): When we write a balanced chemical equation, we show all species present (all reactants and all products): In a net ionic equation, we show only precipitates formed, and the reactants that form them: In a net ionic equation, we show only precipitates formed, and the reactants that form them: The chemicals that stay ions are called spectator ions, And are left out (Na +, NO 3 - ) The chemicals that stay ions are called spectator ions, And are left out (Na +, NO 3 - ) Remember to Balance

Net Ionic Equation Practice Write the net ionic equations for the following: Write the net ionic equations for the following:

Strong/Weak Electrolytes Recall that a solid compound made up of a cation and anion is called a salt. Recall that a solid compound made up of a cation and anion is called a salt. Salts that dissolve completely into their ions when put in water dissociate completely. Salts that dissolve completely into their ions when put in water dissociate completely. Salts that dissociate completely form strong electrolytes – solutions that conduct electricity well. Salts that dissociate completely form strong electrolytes – solutions that conduct electricity well. Some salts only partially dissociate, forming weak electrolytes – solutions that conduct electricity, but do so poorly. Some salts only partially dissociate, forming weak electrolytes – solutions that conduct electricity, but do so poorly.