From today until break….. Get note taking guide for today off front table Mon. 12/19 - Solutions Day one notes, videos and practice Tues. 12/20 - Solutions Day two notes, videos and practice Wed. 12/21 - Solutions HMWK due and quiz… Solutions day 3…. And Ice cream lab!!! (Wahoo!)

Solutions and Equilibrium Unit 9 Solutions and Equilibrium

Solutions Solution - A solution is a homogeneous mixture of two or more substances. What does homogeneous mean? Same; all in one phase, therefore cannot see different particles within the mixture. Solute - Substance that is dissolved into another substance Solvent - Dissolves the solute Aqueous Solution - solute dissolved in water. (Water = solvent)

Solutions Examples Kool-Aid Solute - Kool-Aid powder Solvent - water Chocolate Milk Solute - powder or syrup Solvent - milk

Complete the chart of Solute and Solvent Solution Solute Solvent 2 g of sugar dissolved into 100mL water Gold for jewelry has added Silver, Nickel, and Zinc to make it more durable Jell-O consists of solid particles that were dissolved and then left suspended in water NaCl (aq)

Creating Solutions To create a solution the solute is dissolved into the solvent. Dissolving is a physical process (no rxn takes place) “Likes dissolve Likes” Nonpolar compounds dissolve nonpolar compounds Ex. Oil is nonpolar, and will only dissolve other nonpolar solutes.Polar solvents dissolve polar solutes. Ex. Water dissolves polar compounds, such as salt.

Creating Solutions cont. Example 1: Lava lamps - what is the polarity of the two substances in the lamp? Example 2: Oil and water. Do they mix? What happens when food coloring is dropped on top of oil and water?

Solutions cont. Alcohols - have both a polar AND nonpolar end. Therefore they can dissolve both polar and nonpolar solutes, but NOT ionic compounds.

Dissolving Ionic Compounds Ionic compounds will disassociate into ions when in solution. Ex. NaCl (s) → Na+(aq) + Cl-(aq)

Electrolyte: a compound that conducts an electric current when it is in an aqueous state. Mobile ions are required for the conduction of electric current. Ex. Ionic Compounds (salts), acids, and bases. Electrolytes are essential in your body for cell function. Ex. Ca2+, Mg2+, Na+, Cl-

Dissolving Covalent Compounds Covalent compounds do NOT dissolve into ions. The molecules separate from each other into the solution. Ex. C6H12O6 (s) → C6H12O6 (aq)

Ionic vs Covalent Dissolving

Saturation Unsaturated Solution: the amount of solute dissolved is less than the maximum that could be dissolved. Ex. Earth’s oceans = unsaturated salt solution The ocean can hold a LOT more salt than it actually has in it! Saturated Solution: the solution holds the maximum amount of solute. Supersaturated Solution: contains more solute than the usual maximum amount and is unstable (may release solute suddenly). Created by dissolving solute in the solution at a high temperature then slowly cooling the solution.

Solubility Solubility: The amount of solute that dissolves in a given quantity of a solvent at a specified temperature and pressure.

Factors that Affect Solubility Temperature Solids dissolving in liquids → solubility increases with increasing temperature Think: heating a solid in water will make the solid dissolve quicker Gases dissolving in liquids → solubility decreases with increasing temperature Think: carbonated drinks LOSE their carbonation when heated. OR bodies of water have LESS dissolved oxygen during summer or b/c of thermal pollution

Factors that Affect Solubility cont. Pressure Solubility increases in gases when pressure increases. Think: carbonated drinks Stirring Solute size or surface area

Solubility Curve Notice how temperature affects solubility of solids vs gases Unsaturated solutions fall BELOW the line Saturated solutions fall ON the line Supersaturated solutions fall ABOVE the line

Solubility Curve A solution has 130 g of NaNO3 in 100 g of water at 75oC. Is the solution saturated, unsaturated, or supersaturated? What about 95 g of KNO3 in 100g water at 50oC? How many grams of KCl would dissolve in 100g of water at 90oC? How many grams will dissolve in 200g of water? UNSATURATED SUPERSATURATED 55 g 110 g

Concentration To calculate the concentration of a solution: Molarity (M) = moles of solute liters of solution 3M NaCl = “three molar solution of sodium chloride”

Calculating Molarity What is the molarity of a solution in which 67 g of NaCl are dissolved in 1 L of solution? How many grams of KNO3 should be used to prepare 2 L of a 1 M solution? 67 g NaCl x 1 mole = 1.146 mol 58.44 g Molarity = 1.146 mol 1 L Molarity = 1.146 M 1 M = mol KNO3 2 L 2 mol KNO3 2 mol KNO3 x 101.1 g = 202.2 g KNO3 1 mol

Diluting Solutions When you dilute a solution, you increase the amount of solvent (the number of solute particles stays the same). M1 x V1 = M2 x V2 M = molarity V = volume (in mL or L → must be same for both)

Dilution Calculations A chemist starts with 50.0 mL of a 0.40 M NaCl solution and dilutes it to 1000. mL. What is the concentration of NaCl in the new solution? If you dilute 175 mL of a 1.6 M solution of LiCl to 1.0 L, determine the new concentration of the solution. A chemist wants to make 500. mL of 0.050 M HCl by diluting a 6.0 M HCl solution. How much of that solution should be used? 0.02 M NaCl 0.28 M LiCl 4.16 mL HCl

Get a note taking sheet off the front table Tuesday…. 12-20-16 Get a note taking sheet off the front table Tues. 12/20 - Solutions Day two notes, videos and practice Wed. 12/21 - Solutions and equilibrium HMWK due and quiz… Solutions day 3…. And Ice cream lab!!! (Wahoo!) HMWK: Finish Homework Packet… and study for quiz

Equilibrium Chemical Equilibrium - When the rate of the forward reaction equals the rate of the reverse reaction and the concentration of products and reactants remains unchanged. Bailing Beakers Reversible reaction - A chemical reaction in which the products can react to re-form the reactants.

Le Chatelier’s Principle When a system at equilibrium is placed under stress, the system will undergo a change in such a way as to relieve that stress. Henri Le Chatelier

Explaining Le Chatelier’s Principle When you take something away from a system at equilibrium, the system shifts in such a way as to replace what you’ve taken away. When you add something to a system at equilibrium, the system shifts in such a way as to use up what you’ve added.

Example #1 - Le Chatelier’s Principle A closed container of ice and water at equilibrium. Heat is added to the system. Water/Ice + Energy → What happens to the equilibrium? Shifts to the RIGHT to use up the added energy.

Example # 2 - Le Chatelier’s Principle N2 + 3H2 → 2NH3 In a closed container, more NH3 is added to the system. Which way will equilibrium shift? Equilibrium will shift to the LEFT in order to use up what was added.

Example #3 - Le Chatelier’s Principle A closed container of water and its vapor at equilibrium. Vapor is removed from the system. water + Energy vapor Equilibrium will shift to the RIGHT to replace the vapor.

Example #4 - Le Chatelier’s Principle A closed container of N2O4 and NO2 at equilibrium. The pressure is increased. N2O4 (g) + Energy 2NO2 (g) More pressure shifts to fewer particles. Look for smaller number of moles (total of coefficients) The equilibrium of the system shifts to the LEFT to lower the pressure, because there are fewer moles of gas on that side of the equation.

Measuring Equilibrium At equilibrium the concentrations of products and reactants are constant. We can write a constant that will tell us where the equilibrium position is. Keq = [Products]coefficients [Reactants]coefficients Keq = equilibrium constant Square brackets [ ] means concentration in molarity (moles/liter)

Calculating Equilibrium General equation aA + bB cC + dD

Calculating Equilibrium Calculate the equilibrium constant for the following reaction. 3H2(g) + N2(g) 2NH3(g) If at 25oC there 0.15 mol of N2 , 0.25 mol of NH3, and 0.10 mol of H2 in a 2.0 L container. Calculate Molarity Create Equilibrium equation

Calculating Equilibrium 3H2(g) + N2(g) 2NH3(g) 1. Calculate Molarity 0.15 mol of N2 = 0.075 m N2 2 L 0.25 mol of NH3 = 0.125 m NH3 2L 0.10 mol of H2 = 0.05 m H2 Create Equilibrium equation Eq = .125 2 NH3 0.0751 N2x 0.5 3 H2

Calculating Equilibrium If Keq > 1 Products are favored More products than reactants at equilibrium If Keq < 1 Reactants are favored

Equilibrium Calculations Note: When calculating equilibrium, do NOT include solids and liquids (AKA water.) Only include gases and aqueous solutions. Solids and liquids do not affect the equilibrium. Ex. Write the equation for the equilibrium constant for the following reaction: H2O (g) + C (s) H2 (g) + CO (g) Keq = [H2] [CO] [H2O]

Review Questions What types of compounds would ionize in water? What would happen if we increase the temperature of a solution in which a solid is dissolved in a liquid? What mass of Na2SO4 is needed to make 2.5L of 2.0M solution? Why do oil and water not mix? Write the equilibrium expression. Which direction will equilibrium shift if more CO2 is added? H2CO3 (aq) CO2 (aq) + H2O (l)

Freezing Point Depression - When a solute is added to a solvent, the freezing point of the solvent decreases. Vapor Pressure Lowering - The vapor pressure of a solvent is lowered when a solute is added. Boiling Point Elevation - When a solute is added to a solvent, the boiling point of the solvent increases.