MCAT C/P, B/S and P/S Review 2024/2025 with 100% correct answers
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MCAT C/P, B/S and P/S R]\\\'
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MCAT C/P, B/S And P/S R]\\\'
Increasing the molarity of an ionic solution correct answersIncreases the ability of the solution to conduct electricity b/c solns containing dissolved salts release charged particles into solution that can carry an electric current
The highest measured current at a given voltage during the exp....
Increasing the molarity of an ionic solution correct answersIncreases the ability of the solution to
conduct electricity b/c solns containing dissolved salts release charged particles into solution that can
carry an electric current
The highest measured current at a given voltage during the exp. would most likely be produced by pBS
with which mass ratio of NaCl, KCl and Na2HPO4? correct answers1.5:0.5:1
Q is asking which ratio of PBS by mass would make a solution of the greatest molarity.
Na2HPO4 doesn't dissociate so can be disregarded in comparing molarities.
For any equal mass of each salt, NaCl will always provide more moles. Q boils down to which of these
mixtures has more NaCl present.
PBS already has a set mass of Nacl, KCl and Na2HPO4 so the mass ratio is of mass of each salt compared
to the total mass of PBS. NaCl will always produce more moles when its molar mass is multiplied by an
equal mass.
What are charge carriers in electric circuits? correct answersA charge carrier is a particle that is free to
move, carrying an electric charge, esp. the particles that carry electric charges in electrical conductors.
Charge carriers are different from electron transporters.
After adding the sodium acetate soln, an increased amplitude in the current reading was observed.
Which of the following best explains this phenomenon? correct answersNaCH3COO almost completely
ionizes, providing more charge carriers in the soln. Increasing the number of charge carriers in the soln
causes an increased amplitude in the current reading.
If the lab ran out of ethanol, which of the following chemicals would be most appropriate to use for the
precipitation procedure? correct answersPropanol.
Whole point of using ethanol is to precipitate DNA b/c the added sodium acetate introduces Na+ ions
that interact with DNA's negatively charged phosphate backbone, leaving the DNA too polar to remain
soluble in the substantially less polar ethanol soln. Ethanol is miscible with water and won't form two
phases. Its addition serves to reduce the polarity of the solution.
So we need a molecule that's miscible with water but also non-polar enough to precipitate DNA.
Propanol is most similar to ethanol
, If the exp in Figure 1 was repeated with N2, would it give a different result than having used CO2?
correct answersYes, nitrogen would behave differently b/c of the already high quantities of nitrogen in
the air. Nitrogen makes up the largest proportion of the gases in the air of around 75%. Releasing 6000
ppm of nitrogen into a room would not detectably increase the partial pressure of nitrogen. There would
then be less of a concentration gradient for nitrogen to diffuse down so the concentration would simply
remain constant. The other gases listed would display the same behavior of diffusing out of the room.
Ethanamide undergoes hydrolysis in a test tube containing a solution with a pH of 11. Which of the
following describes what would happen if a strip of moist litmus paper was held above the test tube?
correct answersAmides in alkaline conditions would undergo hydrolysis to form ammonia and the salt of
the corresponding acid, the ethanoic acid. The ammonia gas would then bubble out of the liquid
solution. Ammonium ion would be produced only if the amide were hydrolyzed in acidic conditions.
Physically write out the eq. if the question gives you a reaction.
Effect of decreasing the volume of the system correct answers- favors the side of the equilibrium with
fewer moles of gas b/c the pressure will increase
What would decreasing the temp. of a rxn with positive enthalpy mean? correct answers- removing a
reactant b/c heat in a rxn with positive enthalpy means that heat is on the reactant side
What is considered a small sample size? correct answersFor data that isn't skewed: a small sample size
normally < 10 is sufficient
For data that is moderately skewed: n>=25 (central limit theorem) and may need an even larger sample
size if the data is highly skewed
1) Acid strength increases as the EN of the nonmetal atom increases
- polarity of a X-H bond increases with the EN of the nonmetal atom b/c it withdraws more electrons
away from the hydrogen atom
2) Acid strength increases as the atomic radius of the non-metal atom increases
- strength of the X-H bond decreases as the atomic radius of X increases
- H+ is more easily broken away from a larger atom than a smaller one b/c the e- cloud in a large atom is
more diffuse (smaller the non-metal atom, the more dense the e- cloud)
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