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

Soluble versus insoluble 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 covalent solids (like sugar) dissolve because they are relatively polar.

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

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

Special types of mixtures - 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. Muddy water and Italian salad dressing are good examples of suspensions.

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

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

7 Types of Colloids Page 404 Two groups of colloids: Colloid Type Phases Example 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 Two groups of colloids: Heterogeneous colloids – two phases are clearly seen Homogeneous colloids – appears to be one phase

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

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

The Tyndall Effect

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

What do you think? Is saltwater (NaCl in water) an electrolyte? Is sugar water (C6H12O6 in water) an electrolyte? Conductivity tester (meter) can tell us if a solution is an electrolyte, and sometimes, how strong an electrolyte is.

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

Warm Up I am collecting: Thermo Article Analysis (get it to me by Monday if it isn’t done!) Book Notes- 16.1 and 10.4 Thermo Review Last minute questions?

Solubility Increasing temperature increases the solubility of solids in liquids. Increasing temperature decreases the solubility of gases in liquids! …

Reading Solubility Curves

Solid-Liquid solubility with temperature

Gas-Liquid solubility with temperature

Gases in liquids In addition to cold temperatures, high pressures increase solubility of gases in liquids. 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. (H2O) Other solvents are nonpolar, having no “+” “-” poles Polar solutes tend to dissolve well in polar solvents… Nonpolar solutes tend to dissolve well into nonpolar solvents.

Like Dissolves Like Water is very polar. Does it dissolve polar substances or non polar substance?

Saturation Saturated Solution Unsaturated Solution solution has as much solute in it as it will allow (equal to solubility) Unsaturated Solution more solute can still dissolve into solution (less than solubility) 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 …

Solid-Liquid solubility with temperature

Warm UP Which solute is more soluble at 30C? What is the solubility of KCl at 80 C? How much would you add to 20g of KCl in 200g of water to saturate the solution?

What is the general rule for determining solubility? Solvents Water CCl4 C2H6O- ethanol Solutes I2 NaCl KNO3 Br2 Benzene

Which would be electrolytes when dissolved in water? I2 NaCl KNO3 Br2 Benzene

How did you do on the HW? Get into your small groups and compare answers!

Solubility of KNO3 Lab Number your test tubes 1 – 4. Mass 2.0g, 4.0g, 6.0g and 8.0g into the test tubes… the actual amt doesn’t matter as long as you record the values. Place 5 ml of distilled water into your test tubes. Heat them all up…and wait for them to dissolve. Record the temperature where you see the crystals reforming (saturation point).

Warm Up- Use your Solubility Curve WS to answer the questions on the half sheet!

Would the following be soluble in water? Would they be electrolytes? Hexane- C6H14 MgCl2 NaOH CO2

Electrolyte or nonelectrolyte? Demo Classify the following as a solution, colloid or suspension. 1. NaCl in water? 2. Clay (a compound with Si, C and H) 3. Na2CO3 4. Sugar in water (C6H12O6) 5. Corn Starch (a hydrocarbon) in water Electrolyte or nonelectrolyte?

Concentration - Molarity The “Stoichiometry” of Solutions Concentration the quantitative amount of solute present in a solution 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? 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 grams of HCl are found in 100mL of a 2M solution? 1.5 M “molar” 20 L .3 moles 7.2 grams

Work on the 1st 3 problems- Front and Back…

Warm Up Are the following substances soluble in water? Chlorine- Cl2 CF3I NaCO3 Would they be electrolytes or nonelectrolytes?

Questions on Molarity Packet?

Are all Ionic Compounds Soluble? Let’s look at the solubility rules… These are very important when looking at what happens in double replacement reactions.

Solubility Lab

Warm Up: Predict the products, balance the equation and determine the states of matter NaCl + CaNO3 LiSO4 + SrCl2 BaCl2 + H2S

Solubility Rule Lab Questions on the lab?? Did you… Write the first 30 equations and indicate the states of matter? Identify ALL the precipitates? Answer the questions using complete sentences?

Dissociation and Ions Present 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 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): 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+, NO3-) Remember to Balance

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

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

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

Now you are ready to work on the homework WS…

Strong/Weak Electrolytes 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 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.

Quiz…

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

Let’s make 1.0L of a 2.0M NaCl solution.

Try these!! How many grams of sodium chloride are needed to make a 1.3M solution? How much sodium hydroxide is needed to make a 4.6M solution?

Solution Preparation Use the relationship M1V1=M2V2 By dilution of a standard solution: Use the relationship M1V1=M2V2 2. Calculate volume of the “standard solution” to use to get desired volume of desired molarity solution.

Try these… How much 12 M stock solution is needed to make 500.mL of a 3.5M solution? What is the molarity of a stock solution where you used 200. ml to make 0.5 L of a 2.5M HCl solution.

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