Unformatted text preview: e added 10
ml of the salt solution to her 100 ml of imidazole solution, what would the pH be? Q8. B. (7 points) Question 8. (15 points total)
A student in a biochem lab made a buffer solution using imidazole for studies of a protein. She looked up the
thermodynamics for the ionization reaction: ImH+ → Im + H+ and found ΔG° = +34 kJ mol-1 (chemist’s
standard state), and ΔH° = + 30 kJ mol-1, both at 25° C.
Q8. A. (8 points) She dissolved 0.001 moles of ImH+ and 0.001 moles of Im in 100 ml of water. What will the
pH of the buffer solution be? Q8. B. (7 points)
Before she put her protein into the buffer she realized she needed to add some salt. She found a concentrated
stock solution of sodium chloride that she could add, but it was at a pH of 3 (but no buffer in it). If she added 10
ml of the salt solution to her 100 ml of imidazole solution, what would the pH be? Q2. A (5 points)
Final Exam MCB C100A / Chem C130 Fall 2012
If a sample has a total of 1016 protons, how many will be in the lower energy level at 25° C ?
Question 2 (15 points) Proton NMR spectroscopy exploits the interaction of the magnetic moments of protons with an applied
magnetic ﬁeld, and quantum mechanics dictates that the proton can be in one of just two energy levels. The
interaction of one proton with a typical lab magnetic ﬁeld gives an energy difference of 3.972 x 10-25 J between
the two energy levels.
Q2. B (5 points)
The “spin state”
Q2. A (5 points) of a group of protons in the same molecule can be described by specifying whether each spin
i a sample has a total level, state A, or in the upper energy level, state B. The spins 25° C ?
Ifs in the lower energy of 1016 protons, how many will be in the lower energy level at behave independently of
one another (the spin state of one does not depend on the spin states of the others). For a group of six protons
how many distinct states are there? For example, the two spin states ABBABB and AABBBB are two distinct
states, although they have the same en...
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- Fall '09