Unit 7A: Kinetics

I. Kinetics Kinetics: Collision Theory: - Study of how chemical reactions occur and reaction rates - It is collisions between reactants that allow a reaction to occur - In order for a reaction to occur, there has to be the correct amount of energy and orientation of the collisions How to Speed Up Chemical Reactions (and get a date) Video Clip

Ii. Six factors affecting rate of a reaction 1) Nature of the Reactants: 2) Concentration: 3) Surface Area: - Ionic reactants, especially aqueous, react very quickly (easier to break apart ions) Covalent reactants take a long time (hard to break apart the atoms that are sharing e-) - If the concentration of the reactants increases, then the reaction will occur faster - If the surface area of the reactants increases, then the reaction will occur faster

CHECK FOR UNDERSTANDING 1) Why would putting batteries in the refrigerator make them last longer? Decrease in temperature, decrease in the amount of collisions. 2) At STP, which 4.0 g zinc sample will react fastest with dilute hydrochloric acid? Lump C) bar Powdered D) sheet metal B – powdered – more surface area 3) Which substancee would react fastest with hydrochloric acid? C6H12O6 C) MgCl2 H2O D) SF2 C – ionic compound

Ii. Six factors affecting rate of a reaction 4) Pressure (ONLY EFFECTS FOR GASEOUS REACTANTS) 5) Presence of Catalyst: 6) Temperature: If the pressure of the reactants INCREASES, then the reaction will occur FASTER A substance that increases the rate of a reaction by creating a different pathway. It is NOT used in the reaction equation, so it is NOT a reactant or product. It appears ABOVE the reaction - If the temperature of the reactants INCREASES, then the reaction will occur FASTER

III. Energy changes in chemical reactions absorbed Endothermic Reactions: heat is _______________ from the surroundings and the temperature of the surroundings ___________ General Equation: Using Table _______: Example: N2(g) + O2 (g)  2 NO (g) ∆ H (kJ) = ________ Can be rewritten as: decreases A + B + Heat/energy  C + D I +182.6 kJ N2(g) + O2(g) + 182.6 kJ  2 NO (g) Excess stored energy in the products makes them UNSTABLE and more reactive

III. Energy changes in chemical reactions released Exothermic Reactions: heat is _______________ INTO the surroundings and the temperature of the surroundings ___________ General Equation: Using Table _______: Example: 2 C (s) + 3H2 (g)  C2H6 (g) ∆ H (kJ) = ________ Can be rewritten as: increases A + B  C + D + Heat/energy I - 84.0 kJ 2 C (s) + 3H2 (g)  C2H6 (g) + 84.0 kJ The products have less stored energy making them more STABLE

Think about this (video) A propane gas (gas used in grills) leaks into a room filled with oxygen. Will a reaction occur? Explain why or why not? No. There needs to be a spark/flame to ignite (activate) the propane to react with the oxygen to combust (react)

IV. Potential Energy Diagrams (VIDEO) (ANIMATION) Endothermic Reactions: Energy (heat) is _________ by the reactants, so the net amount of potential energy ________________ absorbed increases Reactants PE (60 kJ) A) Potential Energy (PE) of the Reactants: amount of energy the reactants have

IV. Potential Energy Diagrams Endothermic Reactions: Energy (heat) is _________ by the reactants, so the net amount of potential energy ________________ absorbed increases Activation Energy (130 kJ – 60 kJ = 70 kJ) Reactants PE (60 kJ) B) Activation energy: amount of energy it takes to BREAK EXISTING BONDS and get the reaction STARTED

V. Potential Energy Diagrams Endothermic Reactions: Energy (heat) is _________ by the reactants, so the net amount of potential energy ________________ absorbed increases Activation Energy (130 kJ – 60 kJ = 70 kJ Reactants PE (60 kJ) PE of AC (130 kJ) C) PE of Activation Complex: amount of energy activated complex has

IV. Potential Energy Diagrams Endothermic Reactions: Energy (heat) is _________ by the reactants, so the net amount of potential energy ________________ absorbed increases Activation Energy (130 kJ – 60 kJ = 70 kJ) Reactants PE (60 kJ) PE of AC (130 kJ) PE of Products (110 kJ) D) PE of Products: amount of energy the products have

IV. Potential Energy Diagrams Endothermic Reactions: Energy (heat) is _________ by the reactants, so the net amount of potential energy ________________ absorbed increases Activation Energy (130 kJ – 60 kJ =70 kJ + ∆ H for ENDO (+50 kJ) PE of AC (130 kJ) Products PE (110 kJ) Reactants PE (60kJ) E) Heat of Reaction (∆H) : the NET CHANGE IN ENERGY for the reaction (Difference between REACTANTS and PRODUCTS)

IV. Potential Energy Diagrams Endothermic Reactions: Energy (heat) is _________ by the reactants, so the net amount of potential energy ________________ absorbed increases Reverse Activation Energy (20 kJ) Activation Energy (130-60 = 70kJ) + ∆ H for ENDO (+50 kJ) PE of AC (130 kJ) Products PE (110kJ) Reactants PE (60kJ) F) Activation Energy of Reverse Reaction: amount of energy it takes to get the REVERSE REACTION GOING

IV. Potential Energy Diagrams Endothermic Reactions: Energy (heat) is _________ by the reactants, so the net amount of potential energy ________________ absorbed increases Reverse Activation Energy (20 kJ) Activation Energy (130-60 = 70kJ) + ∆ H for ENDO (+50 kJ) - ∆ H for EXO (-50 kJ) PE of AC (130 kJ) Products PE (110kJ) Reactants PE (60kJ) G) Heat of Reaction (∆H) of Reverse Reaction : the NET CHANGE IN ENERGY for the REVERSE reaction

IV. Potential Energy Diagrams (VIDEO) (ANIMATION) Exothermic Reactions: Energy (heat) is _________ by the reactants, so the net amount of potential energy ________________ RELEASED DECREASES Reverse Activation Energy (150-30 = 120 kJ) Activation Energy (150 -70 = 80kJ) - ∆ H for EXO (- 40 kJ) + ∆ H for ENDO (+40 kJ) PE of AC (150kJ) Products PE (30 kJ) Reactants PE (70kJ)

IV. Potential Energy Diagrams Effects of a Catalyst with Potential Energy Diagrams: Catalysts often _______________a chemical reaction by providing a ___________ with a ____________________. However, the heat of reaction (∆ H) remains_________________ SPEED UP NEW PATHWAY LOWER ACTIVATION ENERGY THE SAME AE without AE with WITH CATALYST

Unit 7B: Solutions

I. What is a solution? Heterogeneous Mixture – Homogenous Mixture – Solutions are examples of _______________ mixtures Solution: Solute: Solvent: Substances in which particles are NOT uniform (example - soil) Substances in which particles are uniform (example: aqueous (aq) solutions) HOMOGENOUS Homogenous mixture of substances in the same physical state Substance that is being dissolved Salt Water (solute) Substance that dissolves the solute (solvent)

I. What is a solution? POLAR IONIC + and - the polar solvent Dissolving and Dissociation: Salt (NaCl) and Water NaCl (s)  Na+ (aq) + Cl- (aq) Dissolving occurs when the solvent is ______________________ Dissociation is when ____________ compounds’ ions get pulled apart by the ________________ end of _____________: POLAR IONIC + and - the polar solvent DISSOLVING ANIMATION

I. What is a solution? Atmosphere (O2, N2, CO2…) Antifreeze Types of Solutions: - Gas with gas: Liquid with liquid: Gas with Liquid: Solid with liquid: Solid with Solid: Atmosphere (O2, N2, CO2…) Antifreeze Soda (CO2 (g) in H2O (l)) Salt water (NaCl (s) in H2O (l)) Alloys: Mixture of metals (brass – copper and zinc)

II. Solubility Factors Amount of solute that will dissolve in solvent Nature of Solute and Solvent (video demo): - Amount of solute that will dissolve in solvent “likes dissolves likes” Solution Type Nonpolar Solvent Polar Solvent Nonpolar Polar Ionic Soluble insoluble insoluble soluble insoluble soluble

II. Solubility Factors ↑ ↑ ↑ ↓ ↑ ↑ 2. Temperature: Solids: ________ temperature, _________ solubility (more solid will dissolve) Gases: ________ temperature, _________ solubility 3. Pressure: Only effects gases in liquids Gases: ________ pressure, ___________ solubility - ↑ ↑ ↑ ↓ ↑ ↑

III. Factors affecting rate of solution ↑ ↑ 1. Size of particles: (_______ surface area, ________ rate of solution) 2. 3. Amount already dissolved: (_______ dissolved, ________ rate) 4. Temperature: Solids and Liquids: _________ temperature, _______ rate - Gases: __________ temperature, ___________ rate - Stirring – more surface area brought into contact more slower ↑ ↑ ↑ ↓

IV. Expressing concentrations A. Saturated: - Solution that contains the maximum amount of solute at a given temperature Saturated solutions are in equilibrium (rate of dissolving = rate of recrystalization)

IV. Expressing concentrations B. Unsaturated: Solution is holding ______________________ If more solute is added, ____________ C. Supersaturated: Solution is holding ____________________ Unstable – ____________________________________ LESS solute than maximum it will dissolve more solute than maximum Addition of more solute will bring it back to a saturated solution Supersaturated solution video

V. Solubility Curves (Found on Table ___ ) G Table G Shows: mass of solute that will dissolve in 100 g (or 100 mL) of water at different temperatures Dilute: __________ amount of solute ______________ Concentrated: __________ amount of solute ____________ What is a salt? SMALL DISSOLVED LARGE DISSOLVED AN IONIC COMPOUND (POSITIVE METAL ION WITH NEGATIVE NONMETAL OR PAI)

V. Solubility Curves (Found on Table ___ ) G How to use the chart: Saturated will be ______________ Unsaturated will be ____________ Supersaturated will be ___________ ON THE LINE BELOW THE LINE ABOVE THE LINE

V. Solubility Curves (Found on Table ___ ) G Table G Practice Questions 1. A solution contains 14 g of KCl in 100. g of water at 40 oC. What is the minimum amount of KCl that must be added to make this saturation solution? 2. How many grams of the compound KCl must be dissolved in 200. g of water to make a saturated solution at 60oC? 3. Identify the following as being saturated, unsaturated, or supersaturated: A) 20 oC and 20 g of KNO3 B) 40 oC and 20 g of KClO3 C) 90 oC and 10 g of NH3 D) 50 oC and 55 g of NH4Cl 4. Ninety grams of NaNO3 is added to 100. G of H2O at 0oC. With constant stirring, to what temperature must the solution be raised to produce a saturated solution with no solid remaining? 39 g – 14 g - = 25 g 45 g X 2 = 90 g unsaturated Supersaturated saturated supersaturated Approx. 22oC

V. Solubility Curves (Found on Table ___ ) G Table G Practice Questions 1. A solution contains 14 g of KCl in 100. g of water at 40 oC. What is the minimum amount of KCl that must be added to make this saturation solution? 2. How many grams of the compound KCl must be dissolved in 200. g of water to make a saturated solution at 60oC? 3. Identify the following as being saturated, unsaturated, or supersaturated: A) 20 oC and 20 g of KNO3 B) 40 oC and 20 g of KClO3 C) 90 oC and 10 g of NH3 D) 50 oC and 55 g of NH4Cl 4. Ninety grams of NaNO3 is added to 100. G of H2O at 0oC. With constant stirring, to what temperature must the solution be raised to produce a saturated solution with no solid remaining? 39 g – 14 g - = 25 g 45 g X 2 = 90 g unsaturated Supersaturated saturated supersaturated Approx. 22oC

VI. How to determine if a compound is soluble (Found on Table ___ ) Ionic compounds can or cannot be soluble (dissolve in water). If it is soluble the phase is ___________, if it is insoluble the phase is ___________ Use Table _____ to identify the phase: Examples: 1) PbCO3______ 2) KNO3 _______ 3) Li2S _______ aqueous (aq) solid (s) F aq s aq

VII. Concentration Parts Per Million (ppm): Equation (See Ref. Tabs.) Tells how much solute is dissolved in a given amount of solvent Ratio between mass of solute and total mass of solution PPM = mass of solute* 1,000,000 mass of solution

VII. Concentration Example 1: Approximately 0.0043 g of oxygen can be dissolved in 100. mL of water at 20oC. Express this in terms of parts per million. Example 2: 2.5 grams of a groundwater solution is found to contain 5.4 x 10-6 grams of the Cu+2 ion. What is the concentration of the copper ion in ppm? PPM = mass of solute x 1,000,000 = 0.0043 g O2 x 106 = 43 PPM mass of solution 100.0043 g PPM = mass of solute x 1,000,000 = 5.4 x 10 -6 x 106 = 2.2 PPM mass of solution 2.5g

VIII. Colligative properties of solutions Properties of solvent that change when a solute is added They depend on the concentration of the solute in solution: _____ ___concentration, _____ _____change Electrolytes: CaCl2 (s)  Nonelectrolytes: C6H12O6 (s)  greater greater Solutions that conduct electricity due to the free-moving ions (mostly ionic compounds) Ca +2 (aq) + 2 Cl -1 (aq) Substances formed from covalent bonding do not dissolve into ions upon entering the water C6H12O6(aq)

VIII. Colligative properties of solutions Boiling Point Elevation: (animation) Example: Salt is added to water when cooking pasta - Higher the concentration of a solution, the higher the boiling point of the solution - The more ionic particles in a solution, the higher the boiling point of the solution In 2 cups of water

CHECK FOR UNDERSTANDING 1) Which of the following solutions will boil at the highest temperature? a) 100 g NaCl in 1000 g of water b) 100 g NaCl in 500 g water c) 100 g NaCl in 250 g of water d) 100 g NaCl in 125 g of water The answer is D because it has the highest concentration: Concentration = mass of solute/mass of solvent. The less solvent there is, the higher the concentration of the solution there will be. As the concentration of solution increases, the boiling point increases.

CHECK FOR UNDERSTANDING 2) Which solution has the highest boiling point? a) 1.0 M KNO3 b) 2.0 M KNO3 c) 3.0 M C6H12O6 d) 2.0 M Ca(NO3)2 The answer is D because it has the most amount of particles when dissolved: 1.0 M KNO3  1 particle of K - and 1 particle of NO3 - = 2 total particles 3.0 M C6H12O6  3 particles of C6H12O6 = 3 total particles 2.0 M KNO3  2 (1 particles of K - and 1 particles of NO3 - ) = 4 total particles 2.0 M Ca(NO3)2  2 (1 particles of Ca – 2 and 2 particles of NO3 - ) = 6 total particles

VIII. Colligative properties of solutions Freezing Point Depression: Example: Salt is added to roads in the winter time - The higher the concentration of a solution, the lower the freezing point of the solution - The more ionic particles in a solution, the lower the freezing point of the solution

VIII. Colligative properties of solutions Which type of solute will have the greatest effect on MP and BP, ionic or covalent? Why? - Ionic, they break apart when in water releasing more particles NaCl  Na + (aq) + Cl – (aq) (2 particles) C6H12O6  C6H12O6 (aq) (1 particle)

CHECK FOR UNDERSTANDING 1) Which of the following solutions will freeze at the lowest temperature? a) 100 g NaCl in 150 g of water b) 100 g NaCl in 600 g water c) 100 g NaCl in 125 g of water d) 100 g NaCl in 250 g of water The answer is C because it has the highest concentration: Concentration = mass of solute/mass of solvent. The more solvent there is, the lower the concentration of the solution there will be. As the concentration of the solution decreases, the freezing point increases.

CHECK FOR UNDERSTANDING 2) Which of the following solutions will freeze at the lowest temperature? a) 100 g C6H12O6 in 500 g of water b) 100 g AlCl3 in 500 g of water c) 100 g KBr in 500 g of water d) 100 g MgF2 in 500 g of water The answer is B because AlCl3 breaks into 4 particles, the most of any of the choices. The more particles that a solute ionizes into, the higher the boiling point will be.