classes-summer07-153A-2ID18-Midterm_I_S07_Key

classes-summer07-153A-2ID18-Midterm_I_S07_Key - Name ID #...

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Name : ________Key__ ________ ID # : _____________________ Signature : _____________________ Summer 2007 Midterm I (100 pt, 50 min) 1
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1) (20 pt) a) Write the reaction for the reversible ionization of water. (3 pt) H 2 O H + + OH - b) Using electron pushing mechanism, show the formation of water from its ion products. (3 pt) H + + OH - H 2 O c) Write the equation for the equilibrium constant (Keq) of water. (3 pt) Keq = [H + ][OH - ] [H 2 O] d) Given the equilibrium constant (1.8x10 -16 M) and concentration (55.5 M) of water, derive and calculate the concentration of OH - at standard conditions. (8 pt) [H + ][OH - ] = Keq[H 2 O] = = (1.8x10 -16 M) (55.5 M) = 1x10 -14 M 2 [H + ] = [OH-] = 1x10 -14 M 2 = 10 -7 M = e) Is this concentration of OH - higher in water or an acidic solution? Explain. (3 pt) Acidic solutions by definition (relative to its equilibration with Keq/Kw of water) have higher [H+] and lower [OH-] relative to water. 2
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2) (31 pt) a) Give 3 letter abbreviations of 7 amino acids with side chains that would not be able to form hydrogen bonds (relative to discussion in this class). (7 pt) Gly Ala Pro Val Leu Ile Phe (Met ok)
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classes-summer07-153A-2ID18-Midterm_I_S07_Key - Name ID #...

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