MISSED MCAT QUESTIONS 110
QUESTIONS AND CORRECT
ANSWERS|| 2024\2025 EXAM
Several families in areas 4 and 5 who read the results of the study
believe that their children have no increased risk of developing thyroid
cancer. Is this conclusion accurate?
A. No, the mutations caused by I-131 exposure may take more than
three years to manifest as cancer.
B. No, I-131 has a half-life of only 8 days.
C. Yes, Table 1 shows that there was no increase in cancer in areas 4 and
5 in years 2013 and 2014.
D. Yes, the radiation given off by I-131 is not mutagenic. - ANSWER-
A is correct. This question requires passage information as well as basic
knowledge about cancer. Cancer is the failure of mutated cells to
,regulate cell division and proliferation in a normal manner. Since
regulatory genes and processes are complex, mutations caused by I-131
exposure may not immediately cause detectable cancer, as the mutated
DNA will disrupt the cell cycle over time. Therefore, it is possible that
children in areas 4 and 5 were exposed to enough I-131 to cause
mutations in the DNA of thyroid cells, but the resulting cancer will take
more than 3 years after the accident to become detectable.
B: The half-life of I-131 is short, but the radiation is still mutagenic. An
8-day half-life is more than sufficient to be absorbed by the body and
possibly damage thyroid DNA.
C: Though this represents a plausible statement about Table 1, it is not
entirely accurate, as region 5 does show an increase of cancer in 2013
compared to 2012. In addition, I-131-induced cancer may develop in
areas 4 and 5 after the conclusion of the study.
D: The third paragraph mentions β-decay as well as gamma radiation.
Gamma rays are ionizing and potentially mutagenic. In addition, β-
particles are able to penetrate living matter and can strike and change the
structure of molecules, including DNA.
*Ignored aspect of the passage in order to support the answer I wanted*
,Another possible method of separating 2-methylundecanal and 2-
methylundecanoic acid could be based on:
A. their differences in the rotation of plane-polarized light.
B. a mass spectrometry analysis.
C. an extraction based on their differing solubilities.
D. the very different scent profiles of each molecule. - ANSWER- C is
correct. Note that the compounds discussed in this question are the
compounds mentioned in paragraph 2, not the enantiomers depicted in
Figure 1. (The compounds that are relevant to this question are pictured
below.) With that said, this question asks about separating an acidic
compound from a fairly neutral one. The carboxylic acid group, if
deprotonated, will be much more soluble in water than the aldehyde
group. Thus, a careful extraction with a dilute weak base (such as a
solution of sodium bicarbonate) would separate these two molecules.
Remember, the more polar a compound is, the higher its solubility in
aqueous solution!
A, B, D: These all represent ways to analyze, or gather information
about, a substance. Analytic techniques are distinct from separatory
techniques, which aim to isolate substances from each other.
*Did not thoroughly read the passage or pay attention to the question
and missed that
the compounds weren't enantiomers*
Boiling chips and vacuum distillation, respectively, are used in
distillations to:
, A. provide nucleation sites that give the liquid a place to start forming
bubbles to prevent superheating; lower the boiling points of the
substances to be distilled.
B. lower the boiling points of the substances to be distilled; work
synergistically with the vacuum system to further lower the boiling
points.
C. lower the boiling points of the substances to be distilled; provide
nucleation sites that give the liquid a place to start forming bubbles to
prevent superheating.
D. provide nucleation sites that give the liquid a place to start forming
bubbles to prevent superheating; speed up the distillation process by
vacuuming the first distillate out of the apparatus. - ANSWER- A is
correct. Let's begin with the first part of this question, the function of
boiling chips. When transitioning from liquid to gas during boiling, the
liquid needs nucleation sites, or places to start forming bubbles. This is
typically achieved either by scratching the inside of the flask or by
introducing boiling chips. This eliminates all options except for A and
D.
Next, remember that boiling occurs when the Pvap of the substance in
question equals the Patm. Typically, we boil substances by increasing
the temperature, thereby increasing Pvap. Alternatively, however, we
can lower boiling point by reducing Patm, which can be accomplished
through the introduction of a vacuum. Vacuum distillation is often used
when components have very high boiling points and would otherwise be
difficult to distill.
B: The boiling chip itself does not alter the boiling point of the liquid.
QUESTIONS AND CORRECT
ANSWERS|| 2024\2025 EXAM
Several families in areas 4 and 5 who read the results of the study
believe that their children have no increased risk of developing thyroid
cancer. Is this conclusion accurate?
A. No, the mutations caused by I-131 exposure may take more than
three years to manifest as cancer.
B. No, I-131 has a half-life of only 8 days.
C. Yes, Table 1 shows that there was no increase in cancer in areas 4 and
5 in years 2013 and 2014.
D. Yes, the radiation given off by I-131 is not mutagenic. - ANSWER-
A is correct. This question requires passage information as well as basic
knowledge about cancer. Cancer is the failure of mutated cells to
,regulate cell division and proliferation in a normal manner. Since
regulatory genes and processes are complex, mutations caused by I-131
exposure may not immediately cause detectable cancer, as the mutated
DNA will disrupt the cell cycle over time. Therefore, it is possible that
children in areas 4 and 5 were exposed to enough I-131 to cause
mutations in the DNA of thyroid cells, but the resulting cancer will take
more than 3 years after the accident to become detectable.
B: The half-life of I-131 is short, but the radiation is still mutagenic. An
8-day half-life is more than sufficient to be absorbed by the body and
possibly damage thyroid DNA.
C: Though this represents a plausible statement about Table 1, it is not
entirely accurate, as region 5 does show an increase of cancer in 2013
compared to 2012. In addition, I-131-induced cancer may develop in
areas 4 and 5 after the conclusion of the study.
D: The third paragraph mentions β-decay as well as gamma radiation.
Gamma rays are ionizing and potentially mutagenic. In addition, β-
particles are able to penetrate living matter and can strike and change the
structure of molecules, including DNA.
*Ignored aspect of the passage in order to support the answer I wanted*
,Another possible method of separating 2-methylundecanal and 2-
methylundecanoic acid could be based on:
A. their differences in the rotation of plane-polarized light.
B. a mass spectrometry analysis.
C. an extraction based on their differing solubilities.
D. the very different scent profiles of each molecule. - ANSWER- C is
correct. Note that the compounds discussed in this question are the
compounds mentioned in paragraph 2, not the enantiomers depicted in
Figure 1. (The compounds that are relevant to this question are pictured
below.) With that said, this question asks about separating an acidic
compound from a fairly neutral one. The carboxylic acid group, if
deprotonated, will be much more soluble in water than the aldehyde
group. Thus, a careful extraction with a dilute weak base (such as a
solution of sodium bicarbonate) would separate these two molecules.
Remember, the more polar a compound is, the higher its solubility in
aqueous solution!
A, B, D: These all represent ways to analyze, or gather information
about, a substance. Analytic techniques are distinct from separatory
techniques, which aim to isolate substances from each other.
*Did not thoroughly read the passage or pay attention to the question
and missed that
the compounds weren't enantiomers*
Boiling chips and vacuum distillation, respectively, are used in
distillations to:
, A. provide nucleation sites that give the liquid a place to start forming
bubbles to prevent superheating; lower the boiling points of the
substances to be distilled.
B. lower the boiling points of the substances to be distilled; work
synergistically with the vacuum system to further lower the boiling
points.
C. lower the boiling points of the substances to be distilled; provide
nucleation sites that give the liquid a place to start forming bubbles to
prevent superheating.
D. provide nucleation sites that give the liquid a place to start forming
bubbles to prevent superheating; speed up the distillation process by
vacuuming the first distillate out of the apparatus. - ANSWER- A is
correct. Let's begin with the first part of this question, the function of
boiling chips. When transitioning from liquid to gas during boiling, the
liquid needs nucleation sites, or places to start forming bubbles. This is
typically achieved either by scratching the inside of the flask or by
introducing boiling chips. This eliminates all options except for A and
D.
Next, remember that boiling occurs when the Pvap of the substance in
question equals the Patm. Typically, we boil substances by increasing
the temperature, thereby increasing Pvap. Alternatively, however, we
can lower boiling point by reducing Patm, which can be accomplished
through the introduction of a vacuum. Vacuum distillation is often used
when components have very high boiling points and would otherwise be
difficult to distill.
B: The boiling chip itself does not alter the boiling point of the liquid.
