CH302 Exam 2-solutions

# CH302 Exam 2-solutions - Version 114 Exam 2 sutcliffe(51630...

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Version 114 – Exam 2 – sutclife – (51630) 1 This print-out should have 28 questions. Multiple-choice questions may continue on the next column or page – Fnd all choices be±ore answering. 001 10.0 points The equilibrium constant ±or the reaction P 4 (s) + 6 Cl 2 (g) 4PCl 3 ( ± ) is K .C a l c u l a t et h ee q u i l i b r i umc o n s t a n o r the reaction 2PCl 3 ( ± ) 3Cl 2 (g) + 1 2 P 4 (s) . 1. 1 K 2. - K 3. K 4. 1 K 2 5. 1 K correct Explanation: 002 10.0 points K c =2 . 6 × 10 8 at 825 K ±or the reaction 2H 2 (g) + S 2 (g) ² ³ 2 S(g) The equilibrium concentration o± H 2 is 0.0020 Mandtha to ±S 2 is 0.0010 M. What is the equilibrium concentration o± H 2 S? 1. 1.02 M correct 2. 0.0010 M 3. 10 M 4. 0.10 M Explanation: K c . 6 × 10 8 [H 2 ] eq =0 . 0020 M [S 2 ] eq . 0010 M 2 (g) + S 2 ² ³ 2 S K c = [H 2 S] 2 [H 2 ] 2 [S 2 ] [H 2 S] = ± K c [H 2 ] 2 [S 2 ] = ± (2 . 6 × 10 8 )(0 . 0020 M) 2 (0 . 0010 M) =1 . 0M 003 10.0 points At 1000 K the equilibrium pressure o± the three gases in one mixture 2SO 2 (g) + O 2 (g) ² ³ 3 (g) were ±ound to be 0.562 atm SO 2 ,0 .101a tm O 2 ,and0 .332atmSO 3 a l c u l a t h ev a l u e K p ±or the reaction as written. 1. 5.83 2. 0.289 3. 0.171 4. 2.64 5. 3.46 correct Explanation: P SO 3 . 332 atm P SO 2 . 562 atm P O 2 . 101 atm K p = P 2 SO 3 P 2 SO 2 · P O 2 = (0 . 332) 2 (0 . 562) 2 (0 . 101) =3 . 46 004 10.0 points Consider the reaction PCl 5 (g) ² ³ PCl 3 (g) + Cl 2 (g) where Δ H =+22 . 1kca l . Equ i l ibr iumsh i ±ts in response to i) increasing the volume ( V )and ii) increasing the temperature ( T ). The equilibrium shi±t will be ( means equilibrium shi±ted ±rom right to le±t and means equilibrium shi±ted ±rom le±t to right). 1. V ; T

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Version 114 – Exam 2 – sutclife – (51630) 2 2. V ; T correct 3. V ; T 4. V no efect; T 5. V ; T Explanation: The reaction is endothermic ( i.e., heat is a reactant) so that increasing the temperature will “push” the reaction to the right (toward the products). When the volume increases, the system will try to expand and Fll the space. It can do that by shi±ting to the right also (the side with the most moles o± gas). 005 10.0 points ²or a given triprotic acid H 3 A, which o± its pK a values usually will be the largest? 1. pK a 0 2. not enough in±ormation 3. pK a 2 4. pK a 3 correct 5. pK a 4 6. pK a 1 Explanation: Typically, ±or polyprotic acids each succes- sive deprotonation event is less spontaneous than the preceding event, and so has a smaller K a and larger pK a associated with it. Conse- quently, the smallest K a and largest pK a will correspond to the Fnal deprotonation, in this case the third. 006 10.0 points One diference between a Lewis base and an Arrhenius base is 1. aLewisbaseisanelectronpairdonorand an Arrhenius base produces hydroxide ions in solution. correct 2. aLew isbaseisane lectronpa iracceptor and an Arrhenius base is a proton acceptor.
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## This note was uploaded on 10/06/2011 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas.

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CH302 Exam 2-solutions - Version 114 Exam 2 sutcliffe(51630...

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