Chem-Phys Comprehensive
Questions with Verified
Answers Graded A+
In the chromatography of the reaction mixture, water absorbed on cellulose functioned as the
stationary phase. What was the principal factor determining the migration of individual
components in the sample?
A.Hydrogen bonding
B.Solute concentration
C.Stationary phase concentration
D.Thickness of paper - Answer: B and D are dumb options. Knock them out.
hydrogen bonding to the stationary phase will determine the relative rate of migration of the
various components in the sample.
When thinking migration, think bonding. If it bonds super well, it isn't going to move very far.
What assumption is being made if scientists conclude that aspartic acid was formed by the
prebiological synthesis in the passage?
A.Aspartic acid is unstable at temperatures below 150°C.
,B.All of the malic acid underwent the dehydration reaction to form fumaric/maleic acid.
C.Compound A and cyanide were available on primitive Earth.
D.The reaction between ammonia and fumaric acid was catalyzed by the presence of water. -
Answer: POE:
D- is wrong. water is not a catalyst
B- some of the magic acid was turned to aspartic acid in the next equation. WRONG.
A- the 150 degrees comes into play when the scientists are doing the actual experiment, NOT
the synthesis.
C- passage has right before the figure of the reaction: "scientists have studied the production of
amino acids under conditions that simulate those of primitive Earth."
^^^^this indicates that C is the right answer.
According to the developed chromatography plate shown below, what is the approximate Rf
value of aspartic acid? - Answer: Rf: distance travelled by analyze/distance traveled by solvent.
2/10---> 0.2
Which of the following statements does NOT correctly describe the dehydration of malic acid to
fumaric acid and maleic acid?
, A.The reaction occurs most readily with tertiary alcohols.
B.The reaction involves the loss of a water molecule.
C.The reaction has a carbocation intermediate.
D.The reaction is stereospecific. - Answer: NOT is the key word.
DEHYDRATION involves:
-loss of a water molecule (cross b out)
-it does have a carbocation (sn1)
-and does like tert substitutions (snl)
D is wrong. Two products are made, therefore it is not stereospecific.
What type of functional group is formed when aspartic acid reacts with another amino acid to
form a peptide bond?
A.An amine group
B.An aldehyde group
C.An amide group
D.A carboxyl group - Answer: C. amide is the other end of the peptide bond!
peptide bond= carboxyl group reacts with amine, making a c=o next to an N which is an amide