test4 - Chem 105b Exam 2 Thursday February 20, 2007...

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Chem 105b Exam 2 Print Name Last, First Thursday February 20, 2007 Last 4 digits SID # Professor Stephen Bradforth TA's Name Questions Points Score Grader 1-5 20 6 15 7 20 8 20 9 25 Total 100 Please Sign Below: I certify that I have observed all the rules of Academic Integrity while taking this examination. Signature: ________________________________________________ INSTRUCTIONS 1. You must show your work to receive credit. You must show your complete working on each of problems 6-9 to receive full credit. 2. If necessary, please continue your solutions on the back of the preceding page (facing you). 3. YOU MUST Use black ink. 4. There are 9 problems on 12 pages. Please count them before you begin.
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1 Chemistry 105 B Midterm 2 Professor Bradforth Spring 2007 You must show your complete working on each of problems 6-9 to receive full credit. State and justify any approximations you make. Useful Physical Constants and Equations T C = T K - 273.15 R = 8.314 J K -1 mol -1 and R = 0.08206 L atm mol -1 K -1 Arrhenius Equation: k = A exp (- E A / RT) - = T R E A k A 1 ) ln( ) ln( Gaseous Equilibria: K p = K (RT) n where n is the sum of the coefficients of gaseous products minus the sum of the coefficients of gaseous reactants. Aqueous Equilibria: Dissociation of an acid in water: HA + H 2 O A + H 3 O + Reaction of a base in water: B + H 2 O HB + + OH Autoionization of water: K w = [ H 3 O + ] [ OH¯ ] = 1.0 × 10 -14 @ 25 ° C pH = - log 10 [ H 3 O + ] pOH = - log 10 [ OH¯ ] Solution of the quadratic equation a x 2 + b x + c = 0 is given by: a ac b b x 2 4 2 - ± - =
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2 Values of K a for Some Common Monoprotic Acids Name Formula K a Hydrogen sulfate ion HSO 4 - 1.2 × 10 -2 Chlorous acid HClO 2 1.2 × 10 -2 Monochloroacetic acid HC 2 H 2 ClO 2 1.35 × 10 -3 Hydrofluoric acid HF 7.2 × 10 -4 Nitrous acid HNO 2 4.0 × 10 -4 Formic Acid HCO 2 H 1.8 × 10 -4 Acetic acid HC 2 H 3 O 2 1.8 × 10 -5 Hydrated aluminum (III) ion [Al(H 2 O) 6 ] 3+ 1.4 × 10 -5 Hypochlorous acid HClO 3.5 × 10 -8 Hydrocyanic acid HCN 6.2 × 10
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test4 - Chem 105b Exam 2 Thursday February 20, 2007...

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