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Term Test 2

Chemistry 123. Term Test 2. Click Here. Notes On This Presentation. This presentation is completely interactive In order for this presentation to work you MUST follow the indicated tabs on each slide Answer the question on a separate piece of paper and compare with the slides

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Term Test 2

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  1. Chemistry 123 Term Test 2 Click Here

  2. Notes On This Presentation • This presentation is completely interactive • In order for this presentation to work you MUST follow the indicated tabs on each slide • Answer the question on a separate piece of paper and compare with the slides • This presentation’s purpose is diagnose what you haven’t understood or what you haven’t attempted • Follow it properly and you will succeed! Next Slide

  3. Section 2.1 Factors Affecting the Rates of Chemical Reactions When Chemists study reactions, they have observed many factors that increase or decrease the over all concentration per unit time. These changes have allowed for advancements in chemical research, specifically in Chemical Kinetics. Next Slide

  4. Section 2.1 CHEMICAL KINETICS By definition, CHEMICAL KINETICS is the study of chemical reactions, specifically looking at the quantitative (numerical/mathematical) study of reaction rates. A REACTION RATE (sometimes referred to as the speed of a reaction) is the change of concentration of reactants or products per unit time. In other words, it is how fast or slow a reaction takes place. It is important to understand that reaction rates allow chemists to differ between slow reactions, like the oxidation of iron into rust, and fast reactions, like the combustion of fire works. Factors Affecting the Rate of Chemical Reactions Next Slide

  5. Section 2.1 NATURE OF THE REACTANTS • The First Factor which affects the Rate of Chemical Reactions is the NATURE OF THE REACTANTS involved in a particular reaction.The best way to understand this factor is to understand possible examples. • IONS (react fast), have strong forces and usually really small (easy to move). • (possibly the fastest reaction) • MOLECULE SIZES, if molecules are large, they have a harder time for specific sites of the molecule to interact with specific sites of other molecule. When smaller, molecules can interact with other molecules easier. • BONDING TYPES, bonds that are stronger (triple bonds) are more difficult to break, thus slower reaction rates. When weak bonds are present (single bonds), it is much easier (compared to the triple bond) to break the bond. Factors Affecting the Rate of Chemical Reactions Next Slide

  6. Section 2.1 REACTANT CONCENTRATIONS • The Second Factor which affects the Rate of Chemical Reactions is the CONCENTRATION of the REACTANTS during a reaction. • HIGHER CONCENTRATION, implies that more molecules will be available for interaction with other molecules, thus increasing the rate. • LOWER CONCENTRATION, implies that less molecules will interact with each other, thus decreasing the rate. • In the video, you see a difference in the concentration of coal particles. Obviously, on the left, there aren’t as many particles compared to the right. Thus it is right to say that the flame on the right is burning more coal than the flame on the left. Thus the rate of the flame on the right is greater because more coal is being burned for the same unit time. Factors Affecting the Rate of Chemical Reactions Next Slide

  7. Section 2.1 TEMPERATURE • The Third Factor which affects the Rate of Chemical Reactions is the TEMPERATURE in which the reaction takes place. • HIGHER TEMPERATURE, implies that molecules will be moving quicker and will interact more often, increasing the likeability that the molecules will interact properly, speeding up the rate of reaction. • LOWER TEMPERATURE, implies that molecules will be moving slower, decreasing the likeability that molecules will interact properly, slowing down the rate of reaction. Factors Affecting the Rate of Chemical Reactions Next Slide

  8. Section 2.1 CATALYSTS The Fourth Factor which effects the Rate of Chemical Reactions is CATALYSTS. A catalyst is meant to speed up a reaction while decreasing the activation energy of a reaction. It is important to note that a catalyst in a reaction will be produced in the reaction, otherwise it is not a catalyst! In biology, ENZYMES are the catalyst of frequent topic because it allows our body to undergo reaction with minimal energy requirements in a efficient manner. In the video you see the dissociation of hydrogen peroxide into water and oxygen with the help of the catalyst manganese dioxide which remains constant in system. The presence of the catalyst increases the rate of reaction which normally would be extremely slow. Factors Affecting the Rate of Chemical Reactions Next Slide

  9. Section 2.1 PHYSICAL STATE OF THE REACTANTS The Fifth and Final Factor which effects the Rate of Reaction is the PHYSICAL STATE OF THE REACTANTS. The physical state of reactants can largely effect the rate of a reaction because it effects whether or not a sufficient amount of reactants can react. Suppose you are trying to burn a log of wood, the combustion of the organic compound will only react on the surface, because the center of the log isn’t it contact with oxygen and fire which is required for this reaction. Thus, the SURFACE AREA of reactants will effect the rate of reaction. Also, a compound in AQUEOUS form allows for movement of the compound in a reaction. Thus, if reactants are dissolved in solution, the rate of reaction will increase. Factors Affecting the Rate of Chemical Reactions Next Slide

  10. Section 2.1 Factors Affecting the Rate of Chemical Reactions QUESTION SECTION QUESTION 1 Chemical Kinetics is the __________ study of reaction _________. Qualitative, Rates Quantitative, Rates Qualitative, Processes Quantitative, Processes Answer

  11. Section 2.1 Factors Affecting the Rate of Chemical Reactions QUESTION SECTION QUESTION 1 ANSWER Chemical Kinetics is the QUANTITATIVE study of reaction RATES. Qualitative, Rates Quantitative, Rates Qualitative, Processes Quantitative, Processes Next Question Next Section

  12. Section 2.1 Factors Affecting the Rate of Chemical Reactions QUESTION SECTION QUESTION 2 (Pulled from winter midterm 2011) Which of the following statements is false? The rate of a reaction usually increases when the concentration of one of the reactants is increased. B. The rate of a reaction is dependent on temperature. C. The rate of a reaction may be increased by certain catalytic agents. D. A reaction will proceed rapidly if the activation energy is large. E. The rate of a reaction describes the change in concentration of a reactant or product with time. Answer

  13. Section 2.1 Factors Affecting the Rate of Chemical Reactions QUESTION SECTION QUESTION 2 ANSWER Which of the following statements is false? The rate of a reaction usually increases when the concentration of one of the reactants is increased. B. The rate of a reaction is dependent on temperature. C. The rate of a reaction may be increased by certain catalytic agents. D. A reaction will proceed rapidly if the activation energy is large. E. The rate of a reaction describes the change in concentration of a reactant or product with time. Next Question Next Section

  14. Section 2.1 Factors Affecting the Rate of Chemical Reactions QUESTION SECTION QUESTION 3 Which one of the following reactions reacts the most rapidly at room temperature. A) 2 H2 + O2 → 2 H2O B) H+ + OH- → H2O (neutralization) C) C12H22O11 (sugar) → 12 C + 11 H2O D) 4Fe + 3O2 → 2Fe2O3 Answer

  15. Section 2.1 Factors Affecting the Rate of Chemical Reactions QUESTION SECTION QUESTION 3 ANSWER Which one of the following reactions reacts the most rapidly at room temperature. A) 2 H2 + O2 → 2 H2O B) H+ + OH- → H2O (neutralization) C) C12H22O11 (sugar) → 12 C + 11 H2O D) 4Fe + 3O2 → 2Fe2O3 *** IONS REACT THE QUICKEST! Next Question Next Section

  16. Section 2.1 Factors Affecting the Rate of Chemical Reactions QUESTION SECTION QUESTION 4 (pulled from the University of Waterloo Chemical Kinetics website) Which one of the following burns easily and why? A) a bar of steel B) steel sheet C) steel wool D) steel pipe Answer

  17. Section 2.1 Factors Affecting the Rate of Chemical Reactions QUESTION SECTION QUESTION 4 ANSWER Which one of the following burns easily and why? A) a bar of steel B) steel sheet C) steel wool D) steel pipe *** Surface Area is greatly increased and allows for the steel to burn. Next Question Next Section

  18. Section 2.1 Factors Affecting the Rate of Chemical Reactions QUESTION SECTION QUESTION 5 Glycolysis, an energy pathway in both anaerobic and aerobic bodies, is undergone in organisms. What is the greatest factor that allows this reaction to occur? A) Catalyst B) Temperature C) Nature of Reactants D) Physical State of Reactants E) Reactant Concentration Answer

  19. Section 2.1 Factors Affecting the Rate of Chemical Reactions QUESTION SECTION QUESTION 5 ANSWER Glycolysis, an energy pathway in both anaerobic and aerobic bodies, is the process of breaking done Glucose into products in organisms. What is the most likely factor that allows this reaction to occur? A) Catalyst B) Temperature C) Nature of Reactants D) Physical State of Reactants E) Reactant Concentration The activation energy of glucose is decreased in every intermediate step and allows for minimal amounts of energy to be used by organisms to break the molecule because organisms do not have the capabilities to combust this sugar. Next Section

  20. Section 2.2 Average and Instantaneous Rates of Change Because the rate of reaction is defined as being the change in concentration over the change in time, it is proper practice to discuss average and instantaneous rates of change. Next Slide

  21. Section 2.2 AVERAGE RATE An AVERAGE RATE of change is quantified by the following equation: This equation allows us to determine the Average Rate when given information in a chart and if given information in a graph. Graphically, the average rate of change is the slope of a line between two points often referred to as the secant. Average and Instantaneous Rates of Change [A] t (in s) Next Slide

  22. Section 2.2 INSTANTANEOUS RATE An INSTANTANEOUS RATE of change is quantified by the following equation: This equation allows us to determine the Instantaneous Rate when given a single concentration at a moment of time. Graphically, the instantaneous rate of change is the tangent of a point. Average and Instantaneous Rates of Change [A] t (in s) Next Slide

  23. Section 2.2 RATE DEFINITION Because the Rate of Reaction can be determined for any reactant or product in a reaction, there must be a way to differ between Reactants and Products. We will define the RATE OF CONSUMPTION to be the rate of which the reactants are used. We will define the RATE OF PRODUCTION to be the rate of which the products are used. Average and Instantaneous Rates of Change Next Slide

  24. Section 2.2 Average and Instantaneous Rates of Change QUESTION SECTION QUESTION 6 What is the Average Rate of Change for the following equation given the following chart of data? Between 10 and 0 for oxygen gas Between 20 and 30 for Glucose (sugar) Answer

  25. Section 2.2 • Average and Instantaneous Rates of Change QUESTION SECTION QUESTION 6 ANSWER What is the Average Rate of Change for the following equation given the following chart of data? Between 10 and 0 for oxygen gas b. Between 20 and 30 for Glucose (sugar) Next Question Next Section

  26. Section 2.2 Average and Instantaneous Rates of Change QUESTION SECTION QUESTION 8 What is the Rate of Production of Carbon dioxide given the following data? From 0 seconds to 10 seconds From 20 seconds to 30 seconds Answer

  27. Section 2.2 • Average and Instantaneous Rates of Change QUESTION SECTION QUESTION 8 ANSWER What is the Rate of Production of Carbon dioxide given the following data? From 0 seconds to 10 seconds From 20 seconds to 30 seconds Next Question Next Section

  28. Section 2.2 • Average and Instantaneous Rates of Change QUESTION SECTION QUESTION 9 (Pulled from winter midterm 2011) Sucrose is fermented to ethanol and carbon dioxide in the following reaction. C12H22O11(aq) + H2O(l) → 4 CH3CH2OH (aq) + 4 CO2(g) If the rate of production of CO2 is 0.250 mol/Ls, then what is the rate of consumption of C12H22O11? 1.00 mol/Ls B) 6.25×10−2 mol/Ls C) 0.250 mol/Ls D) 4.00 mol/Ls E) 0.125 mol/Ls Answer

  29. Section 2.2 • Average and Instantaneous Rates of Change QUESTION SECTION QUESTION 9 ANSWER Sucrose is fermented to ethanol and carbon dioxide in the following reaction. C12H22O11(aq) + H2O(l) → 4 CH3CH2OH (aq) + 4 CO2(g) If the rate of production of CO2 is 0.250 mol/Ls, then what is the rate of consumption of C12H22O11? 1.00 mol/Ls B) 6.25×10−2 mol/Ls C) 0.250 mol/Ls D) 4.00 mol/Ls E) 0.125 mol/Ls *** you must make the mols equivalent in order to find the answer. Next Section

  30. Section 2.3 Rate laws for Chemical Reactions In Chemical Kinetics, we can determine a RATE LAW which is the quantitative relation between the reaction rate and the concentrations of the reactants. This will prove to be useful in determining new properties for Chemical Kinetics. Next Slide

  31. Section 2.3 RATE LAW As explained in the previous slide, a RATE LAW is the quantitative relation between the reaction rate and the concentrations of the reactants. A Rate Law has the following form for the following reaction: Where k is the RATE CONSTANT and x and y are the ORDERS of the reaction in respect to their compounds. In other words, x is the order of the reaction in respect to methane and y is the order of the reaction in respect to oxygen. *** RATE is always in mol/Ls , thus, the rate constant (k) will have different units for different orders. Rate Laws for Chemical Reactions Next Slide

  32. Section 2.3 RATE LAW Suppose the following reaction was undergone: If we wanted to determine the RATE LAW for the following reaction, we would need to obtain data experimentally. This data would include concentrations of all reactants and the INITIAL RATE of these reactants. The initial rate is the instantaneous rate of change for a reaction at time equal to zero. Suppose this data was obtained for the following reaction and was put in the following chart: How can we determine the proper rate law given this information? The method of Initial Rates! Rate Laws for Chemical Reactions Next Slide

  33. Section 2.3 INITIAL RATES CALCULATION Data From Previous Slide STEP 1 Assume the rate law for the given reaction STEP 2 Look for concentrations that remained constant among experiments. STEP 3 Create equations for the following experiments and solve for order. Thus the appropriate RATE LAW is Rate Laws for Chemical Reactions Next Slide

  34. Section 2.3 INITIAL RATES CALCULATION Data From Previous Slide It is now time to determine the value of the rate constant. In order to do this, we must choose any values from a single experiment and solve for k. Rate Laws for Chemical Reactions Next Slide

  35. Section 2.3 Rate Laws for Chemical Reactions QUESTION SECTION QUESTION 10 Given the following Chemical Equations, Determine the Generic Rate law for each: 1) 2) 3) Answer

  36. Section 2.3 Rate Laws for Chemical Reactions QUESTION SECTION QUESTION 10 ANSWER 1) 2) 3) Next Question Next Section

  37. Section 2.3 Rate Laws for Chemical Reactions QUESTION SECTION QUESTION 11 During a chemical reaction, three compounds are combined simultaneously. Calculations are made and the order of reactant A and B are determined. If the order of reactant A is 2 and the order of reactant B is 0, what is the order of reactant C assuming the units on the rate constant are: Answer

  38. Section 2.3 Rate Laws for Chemical Reactions QUESTION SECTION QUESTION 11 ANSWER Thus the order of reactant C is 3 Next Question Next Section

  39. Section 2.3 Rate Laws for Chemical Reactions QUESTION SECTION QUESTION 12 (pulled from midterm) A reaction, A + B → products, was studied using the method of initial rates. The initial rate of consumption of B was measured in three different experiments. Data are provided below: What are the correct units for the rate constants, k for this reaction? Answer

  40. Section 2.3 Rate Laws for Chemical Reactions QUESTION SECTION QUESTION 12 ANSWER *** We must first determine the order. STEP 1 Assume the rate law for the given reaction STEP 2 Look for concentrations that remained constant among experiments. STEP 3 Create equations for the following experiments and solve for order. Thus the appropriate RATE LAW is Continue

  41. Section 2.3 Rate Laws for Chemical Reactions QUESTION SECTION QUESTION 12 ANSWER *** Now that we have the proper Rate Law, we can use it to determine the units on k. *** Thus the answer is C. Next Section

  42. Section 2.4 Integrated Rate Laws Because Rate is equivalent to a differential expression, it is often the case that an integrated form of the Rate Law can be achieved which allows Chemists to use these equations for different types of calculations. Next Slide

  43. Section 2.4 INTEGRATED RATE LAW The Equations achieved by integration of Rate Laws are as follows (These can be found on your Data Sheet): Zero-Order Reactions First-Order Reactions Second-Order Reactions Integrate Rate Law Next Slide

  44. Integrate Rate Law Section 2.4 QUESTION SECTION QUESTION 13 The chemical equation describing the decomposition of Dinitrogen Pentoxide is: The reaction is first-order and the rate constant is k = .0682 min⁻¹. If 1.00 mol of dinitrogen pentoxide is placed in a 2.00L reaction vessel at 352ᵒC, then how long will it take for 25% of the dinitrogen pentoxide to react? Answer

  45. Integrate Rate Law Section 2.4 QUESTION SECTION QUESTION 13 ANSWER *** 25% used means 75% remains *** Thus it will take 4.21 minutes. Next Section

  46. Section 2.5 Analysis of Concentration vs. Time Data When dealing with Orders of reactions, there is often two approaches used to determine the order when data is given in respect to concentration and time. These methods are the Graphical and Algebraic methods. Next Slide

  47. Section 2.5 ALGEBRAIC APPROACH For each of the three orders that are discussed in this course, there is an equation derived from its integrated equation. This equation is simply solving for the rate constant and is useful when given data because for one of the orders we should expect the rate constant to remain constant. Analysis of Concentration vs. Time Data Next Slide

  48. Section 2.5 GRAPHICAL APPROACH The Graphical Approach allows one to determine the order simply by looking at the Graph. All you need to do is remember a few rules and you should be fine at solving these types of problems. For ZERO ORDER reactions, you should expect to see a NEGATIVE linear slope with a plot of [A] vs. t For FIRST ORDER reactions, you should expect to see a NEGATIVE linear slope with a plot of ln[A] vs. t For SECOND ORDER reactions, you should expect to see a POSITIVE linear slope with a plot of 1/[A] vs. t Analysis of Concentration vs. Time Data Next Slide

  49. Analysis of Concentration vs. Time Data Section 2.5 QUESTION SECTION QUESTION 14 Determine the order of the following reaction (using both the graphical and algebraic method) given the following data: Answer

  50. Analysis of Concentration vs. Time Data Section 2.5 QUESTION SECTION QUESTION 14 ANSWER Algebraic Method Graphical Method *** Thus this reaction must be of order 2! Next Section

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