DMA 4/11/11 Write the balanced chemical + equation for the reaction of aluminum and hydrochloric acid (HCl) to produce aluminum chloride and hydrogen gas. + DMA - Monday, May 04, 2009 List three ways you might increase the rate of a chemical reaction? Give some examples. + Tuesday, April 12, 2011 Class Notes - Rates of Reactions Homework Notes and Section Review Chapter 22 DMA 4/12/11 Get your notebook and a pencil and get ready to take some + notes! DMA 4/12/11 Name 2 things you think + could increase the rate at which a chemical reaction happens. + Chemical Kinetics The area of chemistry that concerns reaction rates. + Chemical Kinetics The area of chemistry concerned with the speed at which reactions occur is called chemical kinetics. Reaction rate is the change in concentration of reactants and products in a certain amount of time. Average rate of reaction = Δ [reactant or product] Δ time + Collision Theory Key Idea: Molecules must collide to react. •In order to react molecules and atoms must come in contact with each other. •They must hit each other hard enough to react. •Anything that increase these things will make the reaction faster. Energy Reactants Products Reaction coordinate Energy Activation Energy Minimum energy to make the reaction happen Reactants Products Reaction coordinate Energy Reactants Overall energy change Products Reaction coordinate + Endothermic Reactions + Exothermic Reactions + Catalysts H H Hydrogen bonds to surface of metal. Break H-H bonds H H H H H H Pt surface + Catalysts H H H C C H H H H H Pt surface + Catalysts The double bond breaks and bonds to the catalyst. H H H C H C H H Pt surface H H + Catalysts The hydrogen atoms bond with the carbon H H H C H C H H Pt surface H H + Catalysts H H H H C C H H H Pt surface H + Catalysts + Exothermic Reaction with a Catalyst + Endothermic Reaction with a Catalyst DMA 4/13/11 + What is a catalyst? How does it affect a chemical reaction? Remember to turn in your homework! + Your To-Do List for Today Work In independently and quietly! your books: Read & take notes on “Reaction Rates” on pg. 722-724 Answer Question #1 on pg 731 Read & take notes on 22-2 on pg. 732-737 Answer Questions #1,2,5 on pg. 737 Read & take notes on 22-3 on pg. 738-743 Answer Questions #1-3 DUE TOMORROW!! DMA 4/14/11 + Explain the collision theory. + To Do Today Lab Do activity the lab as written Then, rerun the lab and time it Calculate the rate of the 2 reactions reactant/ time Due at the end of Class today Yesterday’s assignment is due tomorrow. DMA 4/15/11 Name 2 reasons why a scientist + would want to change the rate of a reaction. How could that scientist accomplish this? DMA 4/18/11 Chlorine gas reacts with solid + sodium to produce solid sodium chloride. If 4.85 L of chlorine gas at 308 K and 1.05 atm react with sodium, how many grams of sodium chloride are produced? DMA 4/19/11 + Get out your pre-lab Sit with your lab group To Do Before you Start your lab: 1.Exchange your pre-lab with one person. 2.Grade the other person’s lab according to + the rubric. 3.Get your pre-lab back from who graded yours and fix anything that is missing. 4.Bring your pre-labs to me in your lab groups and I will approve you to begin the lab. DMA 4/20/11 If you were approved to begin yesterday: Get your lab equipment and try to get a couple of trials done. + If you did not get your notebook stamped yesterday: Make sure your pre-lab is done and get it to me for approval so you can begin running your lab. DMA 4/21/11 Define the following: activation energy + catalyst + In the Lab today If you were already approved to begin: Get your lab equipment and get all 10 of your trials done. Be sure to keep careful track of your data You need the change in products(gas) and change in time to calculate the rate of the reaction. If you did not get your notebook stamped yet: Make sure your pre-lab is done and get it to me for approval so you can begin running your lab. DMA #1 4/22/11 What are the seven diatomic Why is it important + molecules? to know what these are? + Post Lab Lab Due Tuesday From your “Composition Book Data Collection Format” Discussion of data collection Graph-I want you to create a graph and attach it into your lab notebook. The graph should have your manipulated variable on the xaxis and your responding variable (rate of reaction) on the yaxis This can be done by hand or computer Calculations of rates of reaction should be present Lab question: answer this as part of your conclusion (the question asked at the beginning of the lab) Conclusion: Claim, Evidence (data), Explain, Conclude + Rate of Reaction Experiments You will design, conduct, analyze, and report on how the rate of a chemical reaction is affected by the factors listed in the next column 1. Type of reactant 2. Temperature You are expected to design your own experiments, not copy those of other lab groups. 3. Concentration of reactant You will need to collect 5 data points for each experiment. + How can we measure the rate of a reaction? In math: rate = distance/time In life: rate = anything changing/time How can we measure the rate of the reaction: Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g) Measure the zinc consumption or gas production versus time. Draw & observe the standard set up for this lab. + Rubber tubing One-hole stopper Glass tube 10ml graduated cylinder Test-tube beaker Standard Reaction Rate Set Up + Data & Observations Keep Track of? Mass of Metal Used for Each Trial (1.0g max) Amount of Acid Used for Each Trial (10 ml max) Temperature (50C max, don’t try to be exact) Time Elapsed for Each Trial (5 minute max) Volume of Gas Produced for Each Trial (10ml max) Observations for Each Trial + Pre Lab Assignment: Question: “What is the effect of _____ on the reaction rate of hydrochloric acid and a particular metal?” Hypothesis: (If, then, because) Manipulated Variable: Responding Variable: Controlled Variables: Materials: Diagram: Validity Measure: (Calibrate? Prevent Contamination?) Procedure: (at least 5 levels, repeated at least 2x) + Experimental Controls? Amount of Acid? Strength of acid? Amount of Metal? When will you stop the trial? + + Factors Affecting Rate Temperature Increasing temperature always increases the rate of a reaction. Surface Area Increasing surface area increases the rate of a reaction Concentration Increasing concentration USUALLY increases the rate of a reaction Presence of Catalysts + Factors Affecting Rate What are some real world examples for temperature? surface Area? concentration? presence of Catalysts? + Catalysis Catalyst: A substance that speeds up a reaction without being consumed Enzyme: A large molecule (usually a protein) that catalyzes biological reactions. Homogeneous catalyst: Present in the same phase as the reacting molecules. Heterogeneous catalyst: Present in a different phase than the reacting molecules. + Catalysts Increase the Number of Effective Collisions + Energy Diagrams 1. Draw and label an energy diagram. Calculate the activation energy and change in energy of the reaction • Reactants – 78.9 kJ • Production – 125.3 kJ • Activated complex – 300 kJ • • • Reactants - 25.1 kJ Products – 35.2 kJ Activated complex – 49.0 kJ + Collision Model Collisions must have enough energy to produce the reaction (must equal or exceed the activation energy). Orientation of reactants must allow formation of new bonds. + 2NO2(g) 2NO(g) + O2(g) Reaction Rates: 1. Can measure disappearance of reactants 2. Can measure appearance of products 3. Are proportional stoichiometrically + Rate of Reaction Lab Rate of Reaction Lab Introduction explain the collision theory and factors affect the rate of the reaction describe how you will investigate your condition how the collision theory and rate of reaction relates to the real world. chemical reaction Hypothesis Variables Procedure + DMA - Test Thursday What is the collision theory? What is an energy diagram? What is an endothermic reaction? What is an exothermic reaction? What is activation energy? What is a catalyst? How do catalysis affect energy diagrams? What factors affect the rate of the reaction? + Reversible Reactions In some chemical reactions, it is possible for the products to react and regenerate the reactants. [Co(H2O)6]2+(aq) + 4Cl-(aq) pink [CoCl4]2-(aq) + 6H2O(l) blue + Use rate of reaction to explain how you can tell if a chemical reaction has reached chemical equilibria. Equilibria Equilibrium exists when two opposing processes occur at the same rate. Even though changes are occuring, there is no overall, or net, change. Equilibria exists when the rate of forward reaction is equal to the rate of reverse reaction. + Le Châtelier’s Principle In 1888, a French mining engineer named Henri Louis le Châtelier discovered something about what happens when a reaction at equilibrium is disturbed. Le Châteleier’s Principle: if a change in conditions is imposed on a system at equilibrium, the equilibrium position will shift in the direction that tends to reduce that change in conditions. Le Châtelier’s Principle If you introduce a change into a system at equilibrium, the system will shift away from the change to reestablish equilibrium. What are two ways to reestablish equilibrium on this teeter totter? + Le Châtelier’s Principle Reactions that reestablish equilibrium shift either to the right (make more products) or to the left (lose products, form reactants). Adding reactants shift to the right. Adding products shift to the left. + Le Châtelier’s Principle Removing chemicals also causes a reaction to have to shift to reestablish equilibrium. Remove products, shift right. Remove reactants, shift left. Le Châtelier’s Principle + There are other ways to force an reaction to reestablish equilibrium. Increasing pressure on one side of a reaction is analogous to increasing concentration of chemicals. Decreasing pressure on one side of a reaction is analogous to decreasing concentration of chemicals. Exothermic/Endothermic Reactions + Exothermic reactions produce heat as a product in addition to the chemical products. Endothermic reactions absorb heat as a reactant in addition to the chemical reactants. Adding or removing heat from some reactions can force the reaction to shift and reestablish equilibrium. The Haber Process In 1913, the German scientist Fritz Haber utilized Le Châtelier’s Principle in a process for making ammonia from nitrogen and hydrogen. Ammonia was used in the manufacture of explosives. The Haber process allowed the Germans to continue manufacturing explosives despite a blockade on necessary materials by German opponents in WWI. Haber Einstein Berlin 1914 Which way will equilibrium shift if the highlighted chemical is increased. 1. NO2(g) N2O4(g) 2. N2(g) + H2(g) NH3(g) 3. COCl2(g) CO(g) + Cl2(g) 4. H2(g) + I2(g) HI(g) 5. C(s) + H2O(g) CO(g) + H2(g) 6. ZnCO3(s) ZnO(s) + CO2 (g) 7. NH4Cl(s) NH3(g) + HCl(g) 8. SO2(g) + O2(g) SO3(g) 9. CO(g) + H2(g) CH4(g) + H2O(g) 10. NaHCO3(s) + HCl(aq) H2O(l) + CO2(g) +NaCl(aq) Which way will equilibrium shift if the highlighted chemical is •NO NO decreased. •N + H NH 2(g) 2(g) 2 4(g) 2(g) 3(g) •COCl2(g) CO(g) + Cl2(g) •H2(g) + I2(g) HI(g) •C(s) + H2O(g) CO(g) + H2(g) •ZnCO3(s) ZnO(s) + CO2 (g) •NH4Cl(s) NH3(g) + HCl(g) •SO2(g) + O2(g) SO3(g) •CO(g) + H2(g) CH4(g) + H2O(g) •NaHCO3(s) + HCl(aq) H2O(l) + CO2(g) +NaCl(aq) + Chemistry DMA 5/7 List three things that you could do to a chemical reaction at equilibrium to disrupt the system. The Law of Chemical Equilibria In 1864, Norwegian chemists Cato Maximillian Guldberg and Peter Waage formulated the Law of Mass Action that describes equilibrium. They established an Equilibrium Expression and an Equilibrium Constant, Guldberg Waage + aA + bB cC + dD Keq = [C]c[D]d [A]a[B]b + CO(g) + 3H2(g) Keq = [C]c[D]d [A]a[B]b Keq = [CH4][H2O] [CO][H2]3 CH4(g) + H2O(g) + Homogenous and Heterogeneous Equilibria Homogenous equilibria occurs when all reactants and products are in the same physical state. Heterogeneous equilibria occurs when reactants and products occurs in different physical states. + Heterogeneous Equilibria NH4NO3(s) Keq = [N2O][H2O]2 N2O(g) + 2H2O(g) + Equilibrium Constant Keq >> 1 at equilibrium, the system consists mostly of products. Keq = 1 at equilibrium, the system contains roughly equal portions of products and reactants. Keq << 1 at equilibrium, the system consists mostly of reactants. Write equilibrium expressions for each + of the following equations: 1. NO2(g) N2O4(g) 2. N2(g) + H2(g) 3. COCl2(g) 4. H2(g) + I2(g) HI(g) 5. C(s) + H2O(g) CO(g) + H2(g) 6. ZnCO3(s) ZnO(s) + CO2 (g) 7. NH4Cl(s) NH3(g) + HCl(g) 8. SO2(g) + O2(g) SO3(g) 9. CO(g) + H2(g) CH4(g) + H2O(g) 10. NaHCO3(s) + HCl(aq) NH3(g) CO(g) + Cl2(g) H2O(l) + CO2(g) +NaCl(aq) DMA 4/25/11 + Name 4 things that can change the rate of a reaction. + To Do Today Turn in Ch 22 notes & questions Work on 22-3 review (tomorrow’s quiz will be similar to this) Create 14-4 a graph- “Heating Curves” read, take notes, answer questions #1-5 Remember, tomorrow Rates of Reactions Lab is due DMA 4/26/11 Turn in your homework: + 1.Ch 22 notes & questions 2.Rates of Reactions Lab 3.22-3 Review + What are molecules doing in each phase?—Sketch the containers and add a description of the molecular motion of each. What happens to each when heated? + Phase Changes Phases at the molecular level Change the of phase- conversion of a substance from one state of matter into another Always involves a change in energy + Phase Changes + Phase Changes Solid → Liquid →Gas Heat of Fusion: Heat required to convert a solid at its melting point to a liquid Heat of Vaporization: Heat required to convert a liquid at its boiling point to a gas. Heat of Sublimation: Heat required to take a substance directly from its solid to its gas state 5 Types of Energy + Kinetic The energy of motion Potential Stored energy Chemical energy inherent in the chemical bonds which hold molecules together. Examples are coal and oil, which have energy potential that is released upon combustion. Thermal/heat the kinetic energy of molecular motion. Measured as temperature and perceived as heat. Nuclear The energy stored in the nucleus of an atom. + To Do Complete the “Phase Change” graphing activity 2 graphs-water and ammonia Do not write on the assignment sheet-only on your graph paper Return the data sheet at the end of class + Phase Change Diagram - Water Note that the temperature of a substance does not change as it is going through a phase change. + Calculating Energy Changes - Heating Curve for Water 140 120 DH = mol x DHfus DH = mol x DHvap Temperature (oC) 100 80 Heat = mass x Dt x Cp, gas 60 40 20 0 Heat = mass x Dt x Cp, liquid -20 -40 -60 -80 Heat = mass x Dt x Cp, solid -100 Time + Definitions Temperature is a measure of the average kinetic energy of the particles in a sample of matter. A joule is the SI unit of heat as well as all other forms of energy. Heat can be thought of as the energy transferred between sample of matter because of a difference in their temperatures. Units for Measuring Heat + The Joule is the SI system unit for measuring heat: kg m 1 J N m 2 s 2 The calorie is the heat required to raise the temperature of 1 gram of water by 1 Celsius degree 1 calorie 4.18 Joules + Latent Heat of Phase Change Molar Heat of Fusion The energy that must be absorbed in order to convert one mole of solid to liquid at its melting point. Molar Heat of Solidification The energy that must be removed in order to convert one mole of liquid to solid at its freezing point. + Latent Heat of Phase Change #2 Molar Heat of Vaporization The energy that must be absorbed in order to convert one mole of liquid to gas at its boiling point. Molar Heat of Condensation The energy that must be removed in order to convert one mole of gas to liquid at its condensation point. + Latent Heat – Sample Problem Problem: The molar heat of fusion of water is 6.009 kJ/mol. How much energy is needed to convert 60 grams of ice at 0C to liquid water at 0C? 60 g H 2O 1 mol H 2O 6.009 kJ 20.00 kiloJoules 18.02 g H 2O 1 mol Mass of ice Molar Mass of water Heat of fusion + Calculating Energy Changes Heating Curve for Water 140 120 DH = mol x DHfus DH = mol x DHvap Temperature (oC) 100 80 Heat = mass x Dt x Cp, gas 60 40 20 0 Heat = mass x Dt x Cp, liquid -20 -40 -60 -80 Heat = mass x Dt x Cp, solid -100 Time + Specific Heat The amount of heat required to raise the temperature of one gram of substance by one degree Celsius. + Calculations involving Specific Heat cp = ___q__ m x DT OR q = cp x m x DT cp = Specific Heat q = Heat lost or gained DT = Temperature change + Specific heat of ice = 2.092 J/g°C Specific heat of water = 4.184 J/g°C Specific heat of steam = 2.013 J/g°C Heat of vaporization = 2260 J/g Heat of fusion = 334 J/g + Practice Problems Calculate the energy released if 10 grams of steam at 110℃ is cooled to -20 ℃. + Table of Specific Heats + A calorimeter is a instrument that measures the energy absorbed or released as heat in a chemical or physical reaction. + Specific Heat The amount of heat required to raise the temperature of one gram of substance by one degree Celsius. + Calculations involving Specific Heat cp = ___q__ m x DT OR q = cp x m x DT cp = Specific Heat q = Heat lost or gained DT = Temperature change + Table of Specific Heats