SamExamChem26Unit3v5-2 - Chemistry 26 Sample problems for...

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Chemistry 26 – Sample problems for Unit 3 (The actual exam will provide more space to show your work. Also, this practice exam is longer than the actual exam.) In addition to the following problems, Problems similar to those in the homework may also appear on the exam. Equations/Data: Rate = k Rate = k[A] Rate = k[A] 2 [A] = -kt + [A] o ln[A] = -kt + ln[A] o 1/[A] = kt + 1/[A] o t ½ = [A] o /2k t ½ = ln(2) /k t ½ = 1/k[A] o k = Ae - Ea/RT Avogadro's number = 6.022 x 10 23 R = 8.314 J/mole K S surr = - H/T G = H - T S G = G ° + RTlnQ G ° = - RTlnK K = o C + 273.15 1) The balanced equation for the reaction of bromate ion with bromide in acidic solution is given by: BrO+ 5Br  + 6H +    3Br 2  + 3H 2 O At a particular instant in time, the value of – [Br ]/ t  is 2.0  ×  10 –3  mol/L   s. What is the value  of  [Br 2 ]/ t  in the same units? 2) Consider the reaction X   Y + Z Which of the following is a possible rate law? a) Rate =  k [X] b) Rate =  k [Y] c) Rate =  k [Y][Z] d) Rate =  k [X][Y] e) Rate =  k [Z] 3) The following data were obtained for the reaction of NO with O 2 . Concentrations are in molecules/cm and rates are in molecules/cm 3    s. [NO] 0 [O 2 ] 0 Initial Rate × 10 18 × 10 18 2.0  ×  10 16 × 10 18 × 10 18 8.0  ×  10 16 × 10 18 × 10 18 18.0  ×  10 16 × 10 18 × 10 18 4.0  ×  10 16 × 10 18 × 10 18 6.0  ×  10 16  Show your work and find the rate law, including the value of k and the exponents. 4) For a certain reaction, Rate = k [Fe(CN) 6 3– ] 2 [I ][Fe(CN) 6 4– ][I 2 ] a) What is the order of the reaction with respect to I-? b) What is the order of the reaction with respect to Fe(CN) 6 3– ? c) If acid (H+) is known to be a reactant in the overall reaction, what is the order of the reaction with  respect to H + ? d) What is the overall order of the reaction?
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5) For this reaction: H 2 O 2 + 3I - + 2H + I 3 - + 2H 2 O The rate law is: Rate = k[H 2 O 2 ][I - ] Two mechanisms are proposed: I. H 2 O 2  + I -    H 2 O + OI - OI -  + H +    HOI HOI + I -  + H +    I 2  + H 2 O I 2  + I -    I 3 - II. H 2 O 2  + I -  + H +    H 2 O + HOI  HOI + I -  + H +    I 2  + H 2 O I 2  + I -    I 3 - Which of the following describes a potentially correct mechanism? a) Mechanism I with the first step the rate determining step. b) Mechanism I with the second step the rate determining step. c)
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SamExamChem26Unit3v5-2 - Chemistry 26 Sample problems for...

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