Test 1 - Spring 05

# Test 1 - Spring 05 - ~6.5 5 A simple pathway has two steps...

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These are some problems to help you practice some of the math related questions on the first exam. Please do not ask questions on how to do the problem if you have not first attempted to do the problem a few times. The TA’s will not solve the problems for you. The answers to the problems are at the end of the problem in bold. 1. What is the pKa value of an acetic acid buffer system which has a pH of 5.0, the CH 3 COOH is 10mM and the CH 3 COO - is 100mM? ( 4 ) 2. What is the final pH when you mix 400mL of 0.20M HCl with 400mL of 0.15M NaOH?( 1.6 ) 3. Calculate the ratio of HPO 4 2- /H 2 PO 4 - (pK=6.7) at pH 5.7, 6.7, and 8.7.( 0.1, 1, 100 ) 4. Calculate the isoelectric point of glu-ala-arg-tyr.(
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Unformatted text preview: ~6.5 ) 5. A simple pathway has two steps: A ↔ B ↔ C ∆ G o' for A ↔ B = +11.4 kJ/mol, and Keq is 10-2 ∆ G o' for B ↔ C = -22.8 kJ/mol, and Keq is 10 4 a. What is the standard free energy change for conversion of A to C? __--------11.4 ____ kJ/mol b. Write an equation specifying the free energy change ( ∆ G) of the first reaction from A to B, taking into account concentrations of reactant and product: ∆ G = ∆ G o' + RTln(B/A) c. At equilibrium what are the concentration ratios B/A, C/B, and C/A? (Hint: Base your calculation on the equilibrium constants.) B/A= 10-2 _ C/B= 10 4 ____ C/A= 10 2 ____...
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