exam2solution_pdf - Version 026 Exam 2 Sutcliffe (52440) 1...

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Unformatted text preview: Version 026 Exam 2 Sutcliffe (52440) 1 This print-out should have 26 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. USEFUL: K C = K P (RT) ( n) 001 10.0 points Pick the name and formula that do NOT match. 1. HC 2 H 3 O 2 : acetic acid 2. H 2 SO 3 : sulfurous acid 3. H 3 PO 4 : phosphoric acid 4. HF : fluoric acid correct Explanation: HF is hydrogen fluoride. In aqueous solu- tion, HF is known as hydro fluor ic acod. C 2 H 3 O 2 is the acet ate ion so HC 2 H 3 O 2 is acetic acid. PO 3 4 is the phosph ate ion so H 3 PO 4 is phosphor ic acid. Sulfur ic acid is H 2 SO 4 . Sulfur ous acid has one fewer oxygen atom, so its formula is H 2 SO 3 . 002 10.0 points K c = 47 at some temperature for the reaction H 2 (g) + I 2 (g) 2 HI(g) . If 33 . 2 mol of HI are introduced into a 10.0 liter vessel, how many moles of I 2 are present at equilibrium? 1. 5 . 62353 mol 2. 3 . 74902 mol correct 3. 7 . 49803 mol 4. 4 . 49882 mol 5. 37 . 4902 mol 6. 1 . 87451 mol Explanation: K c = 47 V vessel = 10.0 L n HI = 33 . 2 [HI] ini = 33 . 2 mol 10 L = 3 . 32 M H 2 (g) + I 2 (g) 2 HI (g) ini, M 3 . 32 , M x x- 2 x eq, M x x 3 . 32- 2 x K c = [HI] 2 [H 2 ] [I 2 ] = 47 (3 . 32- 2 x ) 2 x 2 = 47 3 . 32- 2 x x = 47 3 . 32- 2 x = 47 x x = 0 . 374902 n I 2 = (10 . 0 L) [I 2 ] = (10 . 0 L) parenleftbigg . 374902 mol L parenrightbigg = 3 . 74902 mol 003 10.0 points K c = 2 . 6 10 8 at 825 K for the reaction 2 H 2 (g) + S 2 (g) 2 H 2 S(g) The equilibrium concentration of H 2 is 0.0020 M and that of S 2 is 0.0010 M. What is the equilibrium concentration of H 2 S? 1. 10 M 2. 0.0010 M 3. 1.02 M correct 4. 0.10 M Explanation: K c = 2 . 6 10 8 [H 2 ] eq = 0 . 0020 M [S 2 ] eq = 0 . 0010 M 2 H 2 (g) + S 2 2 H 2 S K c = [H 2 S] 2 [H 2 ] 2 [S 2 ] Version 026 Exam 2 Sutcliffe (52440) 2 [H 2 S] = radicalBig K c [H 2 ] 2 [S 2 ] = radicalBig (2 . 6 10 8 ) (0 . 0020 M) 2 (0 . 0010 M) = 1 . 0 M 004 10.0 points A solution of 0.2 M boric acid is prepared as an eye wash. What is the approximate pH of this solution? For boric acid K a = 7 . 2 10 10 . 1. pH = 5 correct 2. pH = 4 3. pH = 6 4. pH = 7 5. pH = 3 Explanation: 005 10.0 points For the heterogeneous reaction 2 MnO 2 (s) 2 MnO(s) + O 2 (g) , the equilibrium constant expression for K c is which of the following? 1. K c = [MnO 2 ] [MnO] [O 2 ] 2. K c = 1 [O 2 ] 3. K c = [MnO] [O 2 ] [MnO 2 ] 4. K c = [O 2 ] correct 5. K c = k [MnO 2 ] Explanation: For heterogeneous reactions, only gaseous reactants and species are taken into considera- tion when writing K c expressions. Therefore, K c = [O 2 ]....
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This note was uploaded on 10/25/2010 for the course CH 302 taught by Professor Holcombe during the Fall '07 term at University of Texas at Austin.

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exam2solution_pdf - Version 026 Exam 2 Sutcliffe (52440) 1...

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