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CHEM102 Chapter Notes - Chapter 16.1: Reaction Rate, Collision Frequency

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9 Feb 2017

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CHEM102 Full Course Notes

CHEM102 Full Course Notes

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Chemical kinetics: the study of the rates and mechanisms of reactions. Typically fast reaction rates: neutralization, precipitation, explosion. Slow reaction rate: many reactions, ripening of a fruit, human aging, formation of coal. We can control 4 factors: concentration of reactants, physical state of reactants, temperature of reaction, use of a catalyst, concentration: molecules must collide to react. More molecules present = more frequent collisions = more reaction. Reaction rate is proportional to the number of collisions which depends on the concentration of reactants: physical state: molecules must mix to collide. When in the same phase, random thermal motion brings them into contact and stirring mixes them. When they are in different phases, contact occurs only at the interface vigorous stirring or grinding. More surface area of solid/liquid reactant = more contact = more reaction: temperature: molecules must collide with enough energy. Temperature increases the frequency and energy of collisions. Rate is proportional to collision frequency and temperature.

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Related Questions

Need help with 5. âCalculate molar concentrations of KIO3 and NA2SO3 for solutions A-Gâ on page 113 please!! Solution #1 (KIO3) and solution #2 (Na2SO3) were both diluted with distilled water to 50mL and mixed together to form solution.....density of KIO3=4.28g/L and Na2SO4=1.01g/L. Thank you!!

ENT ives To determine equilibrium concentrations for species in solution . Examine temperature effects on reaction equilibrium Investigate the shift in equilibrium from different stresses on a system kills . Use colorimeter to determine unknown solution concentrations ced .Preparing temperature baths to change reaction conditions tionEquilibrium is defined as a state in which the concentrations of both the reactants and products have no tendency to change with time. We can restate this by saying that the rate of the forward reaction is equal to the rate of the reverse reaction. Recall that with rate we are simply defining how fast a reaction is proceeding, a speed at which the reaction proceeds. Take note that when writing an equilibrium expression, pure liquids (denoted by l or 2) and pure solids (denoted by s) are omitted. Typically we express the equilibrium by K or Kp where c and p denote either concentration or partial pressure respectively. We refer to this value of K, or Kp as an equilibrium constant For any reaction, Kc can be written as the product of the concentration of products, raised to their stoichiometric coefficients, divided by the product of the concentration of the reactants raised to their stoichiometric coefficients. See Equation (5-1) below for an example: aA(aq) + bB(aq-cC(aq) + dD(aq) (5-1) A] [B]b As mentioned before, K, or K, are equilibrium constants meaning that they will have the same value unless temperature is changed. This brings in two important ideas 1) We can perturb the equilibrium concentrations of a reaction, say [A] for instance which will cause the other concentrations to shift so that K for the reaction remains constant. 2) If we change temperature, we will either increase or decrease our value of K depending on the specific reaction we are examining. Determining K, and Equilibrium Concentrations During lecture we often discuss the idea of using ICE tables as a method for organizing and calculating concentrations of reactions as they proceed towards equilibrium. In a typical ICE table you need to know initial concentrations and the magnitude of K to determine the equilibrium concentrations. Alternatively, if you know the equilibrium concentrations for a reaction you can calculate K. For this experiment we will be examining a complex ion formation, when iron(III) ion

For a reaction aA rightarrow Products, [A]_o = 13 M, and the first two half-lives are 35 and 70 minutes, respectively, a) Write the rate law for this reaction. b) Calculate k. c) Calculate [A] at t = 335 minutes The Model of Chemical Kinetics represents the reaction rate constant as: k = (2p) times exp(-Ea/RT). What does each variable in the equation mean- that is, in regard to their contribution towards the reaction rate constant? In other words, what does each variable actually mean/refer to? Chemists commonly use a rule of thumb that an increase of 10 K in temperature doubles the rate of a reaction. What must the activation energy be for this statement to be true for a temperature increase from 63 degree C to 73 degree C? ln(k_2/k_1) = E_a/R(1/T_1 - 1/T_2) (i) What is a catalyst? (ii) What are the two types of catalysts? Explain specifically why they are different? (iii) What is one example of each type of catalyst? (i) What does it mean when a reaction is in chemical equilibrium? Specifically, within the context of reactants? products, and the forward and reverse reaction rates, what does chemical equilibrium mean? (ii) What is Le Chateleir's Principle? Within the context of reactant/product concentration, temperature, and pressure, how does Le Chatelier's Principle predict a reaction will respond to variations in reactant, product concentration, temperature, and pressure. (i) For the given reactions: N_2(g) + 3H_2(g) harr 2NH_3(g), H_2O(g) + CO(g) harr H_2(g) + CO_2(g), HCN(aq) harr H^+(aq) + CN^-(aq), 2KClO3(s) harr 2KCl(s) + 3O_2(g) and 2H_2 O(l) harr 2H_2(g) + O_2(g). Write the equation that governs each of their equilibrium rate constant K (ii) If N_2(g) + 3H_2(g) harr 2NH_3(g)'s (at 25 degree C) has K = 25, what would K be (at 25 degree C) for 2NH_3(g) harr N_2(g) + 3H_2(g)? (iii) What would K be if [5 times (N_2(g)+3H_2(g) harr 2NH_3(g)]? (i) For N_2(g) + 3H_2(g) harr 2NH_3(g): P_NH3: 1.9 times 10^-1 atm, P_N2 = 8.9 times 10^-2 atm, P_H2 = 1.9 times 10^-2 atm, what is K_p? (ii) Using K_p, calculated in the previous step, what is K at 45 degree C, where K_p = K(RT)^Delta n? (R = 0.08206 L atm/mol K). What is the difference between homogeneous and heterogeneous? (ii) If K is larger than 1, does the equilibrium life farther to the right (favoring the production of products) or to the left (favoring reactant formation)? (iii) If K is less than 1, does the equilibrium life farther to the right (favoring the production of products) or to the left (favoring the production of reactants)?