First and Last Name ______________________________ SID __ __ __-__ __ __-__ __ __
R. Lannan _________ ___ _ CHEM 153A___________ _Mon, April 22, 2024
Midterm 1
Instructions (please read carefully)
1. The exam consists of 8 questions (11 pages total)
2. Pen is preferred but if you use a pencil you MUST write dark
3. Take the time to write your name and ID on EVERY page (points will be deducted
otherwise!)
4. Do NOT write on the back of any page of the exam as we don’t scan the backs of pages.
If you cannot fit your answer in the provided space, write your answer on Page 11.
5. If you are in need of assistance, please raise your hand quietly. Do your best!
________________________________________________________________________
1
, First and Last Name ______________________________ SID __ __ __-__ __ __-__ __ __
1. Amino acids (7 + 1 pts)
a. You have a solution containing the following species at the stated
concentrations.
at 0.06 M at 0.01 M
i. (2 pts) Is this a buffer system? Why or why not?
yes no Buffer system because ratio is 6:1 (lower than 10:1)
ii. (3 pts) What pH is this solution at? (show your work!)
pH = 2 + log(0.01/0.06) pH = 1.22
b. (+1 serious bonus) If a solution of arginine was at a pH of 12.5, what
would be the net (averaged across the population) charge per molecule?
net charge = -0.5
c. (2 pts) When organizing data from lab you realize you have unlabeled data
from a number of amino acid titrations. Which amino acid titrated with
strong base produced the following plot?
Glu His Leu
2
R. Lannan _________ ___ _ CHEM 153A___________ _Mon, April 22, 2024
Midterm 1
Instructions (please read carefully)
1. The exam consists of 8 questions (11 pages total)
2. Pen is preferred but if you use a pencil you MUST write dark
3. Take the time to write your name and ID on EVERY page (points will be deducted
otherwise!)
4. Do NOT write on the back of any page of the exam as we don’t scan the backs of pages.
If you cannot fit your answer in the provided space, write your answer on Page 11.
5. If you are in need of assistance, please raise your hand quietly. Do your best!
________________________________________________________________________
1
, First and Last Name ______________________________ SID __ __ __-__ __ __-__ __ __
1. Amino acids (7 + 1 pts)
a. You have a solution containing the following species at the stated
concentrations.
at 0.06 M at 0.01 M
i. (2 pts) Is this a buffer system? Why or why not?
yes no Buffer system because ratio is 6:1 (lower than 10:1)
ii. (3 pts) What pH is this solution at? (show your work!)
pH = 2 + log(0.01/0.06) pH = 1.22
b. (+1 serious bonus) If a solution of arginine was at a pH of 12.5, what
would be the net (averaged across the population) charge per molecule?
net charge = -0.5
c. (2 pts) When organizing data from lab you realize you have unlabeled data
from a number of amino acid titrations. Which amino acid titrated with
strong base produced the following plot?
Glu His Leu
2
