AAMC Chem/Phys Q Banks

Question 1

V/m = ?

Answer 1

it reads as voltmeter and can be:

N/C

1 V = 1 J/C

1 J = 1 N•m

so, 1 J/C x 1/m = 1 N•m/C x 1/m = N/C

Question 2

given:

60 million nuclei of americium with a half life of 430 years.

Answer 2

to solve half-life questions, ask

“How many cycles of halving does it take to get from quantity A (60 million nuclei) to quantity B (3.75 X10⁶)”

then multiply that number of cycles by the half life to get total number of years

Question 3

Answer 3

Atomic number= number of protons

Mass number= protons + neutrons

Atomic weight = the average mass of all the isotopes of a certain type. It is a weighted average that takes into account the abundances of all of the different isotopes

*mass number and atomic weight are not the same although they can be effectively treated the same when isotopes are not discussed. In the phrase “Carbon-14” the 14 would be describing the mass number/atomic mass, but the atomic weight would not change from it’s calculated average of 12.

Changes in neutron numbers, as occurs in radioactive decay, are able to change the mass number of atoms, inasmuch as the mass number is protons+neutrons (since proton number does not change, if neutron number changes, therefore mass number changes).

This question is asking for the thing that makes them share chemical behavior. This behavior depends directly on the activity of its electrons such as bonding and electron interactions. Since electrons are equal in number to the number of protons/atomic number (think of the periodic trends and the fact that the proton number fixes each chemical element in place in that table), therefore, the atomic number/proton number is what isotopes share that give them the same chemical behavior.

Question 6

Answer 6

Question 7

Answer 7

850 N/m2

I got this wrong because I forgot to subtract the surface pressure which is 50 N. Instead I kept it on there, which meant that when I doubled the pressure (for double the density d/t proportionality between density and pressure) I double the 50 surface pressure, which in fact would not be doubled since it is unaffected by the new density

Question 8

What happens to a piece of a substance in solid state at it’s exact melting point when a flame is applied for a split second?

Answer 8

the melted substance does not change its temperature until all of the metal has melted, this is because melting occurs at a constant temperature and in phases. The latent heat of fusion is what converts it from solid to liquid even though the temperature itself does not change

Question 9

T/F: the electrons in an atom with partially filled orbitals can jump to a higher energy orbitals by absorbing photons. This produces color

Answer 9

True, see the question, correct answer is selected

Question 10

solve

Answer 10

C turn blue because it reacts with water to form OH-

Question 11

what does this notation indicate and what do you do with it mathematically?

Answer 11

it means hydration. the 6 number indicates the max number of water molecules that can be incorporated into the chrystaline structure of the compound during solvation.

mathematically, just treat them both like reactants. the MW was compute from simply addition (NOT multiplication)

Question 14

How many moles of Ni in a 7 g sample of NiSO₄ •6H₂0 (MW 262.84) dissolved in enough water to make 50mL of a solution.

^how do you solve this?

Answer 14

Answer: 6/262.84 = 0.025

(the number of liters doesn’t effect number of moles)

my instinct is to always try to divide the weight by the molecular weight of just the atom I’m trying to find (e.g. 6.57/58 for nickel) But that is WRONG.

6/262.84 gives you the number of moles of the entire molecule OR the number of moles of each individual component of NiSO₄ because moles is just the number of them that exists and whether they are separate or apart, they exist in units of moles.

analogy: If I’m walking with sean we are a couple and there is 1 of us, but if I am walking by myself I am not a couple but there is still 1 of me. either way there’s 1 (where 1 would be the number of moles in this scenario)

Question 15

CO₃^2- will react with a proton source (HCl) to form ?

Answer 15

CO₂ and OH^-

Question 16

how do you solve this?

Answer 16

since the pKa is constant for a given reaction, you know you can plug it into an equation. The other piece you plug in is pH, since the passage says it was buffered to a pH of 8.7. Since it’s asking about the concentration in the buffer solution (ie the concentration at THAT given pH) all you have to do is plug in the numbers in to the Henderson Hasselback equation

Correct answer is C: 100:1

Question 17

What is the conversion factor for determining the number of cal provided by a given subtance.

Answer 17

1 cal/g °C

example:

Question 18

ionization energy

Answer 18

Question 19

T/F: atoms in the periodic table are all neutral by definition

Answer 19

true

so, the atomic number (eg 6 for carbon) will always indicate the number of protons and the number of electrons.

the number of neutrons is determined by subtracting the # protons from the mass number

notice that Sr²⁺ is not neutral in chemical reactions, but is neutral in its theoretical position within the periodic table

Question 20

What method do you use to solve this without having to write out all the possible combinations?

Answer 20

n! (factorial)

where n=3

possible combos: 3 x 2 x 1 = 6

Question 21

T/F: most elements are metals

Answer 21

Question 22

The compound with the greatest difference in ______________ between the metal and nonmetal atom has the most ionic character

Answer 22

electronegativity

Question 23

a non-metal bonded to a non-metal will be a covalent/ionic bond

Answer 23

covalent

Question 24

avogadro’s number

Answer 24

for MCAT, just use 6 x10²³

Question 25

what is this?

Answer 25

benzoquinone

Question 26

what is this?

Answer 26

hydroquinone

Question 27

the work function is given as 3.4eV in this passage. Flip for question

Answer 27

E_photon =hf

and KE = E_photon - E_initial

E_initial is represented by the “work function”

Question 28

Answer 28

this represents a different way to solve the problem from the TPR method.

Question 29

In addition to the question posed, what does the V with a circle around it represent on this diagram?

Answer 29

it represents a voltmeter (reading the resistance across the Resistors that came before)

Question 30

what is this?

Answer 30

pyrophosphate

Question 31

what is this?

Answer 31

phosphonic acicd

Question 32

What is a phosphatide?

Answer 32

any of a class of compounds that are fatty acid esters of glycerol phosphate with a nitrogen base linked to the phosphate group..

Question 33

what class of macromolecules does this belong to?

Answer 33

phosphatids, to which phospholipids also belongs

Question 34

What equation to use to solve this?

Answer 34

even though the equation to use is

ΔG_actual = ΔG⁰’ – RTlog[C][D]/[A][B],

if no ΔG_actual is provided, you can assume there is no difference between the two ΔG’s and you can simplify equation to ΔG⁰’ = – RTlog (K_eq)

_{ΔG⁰’ = ΔG in standard conditions}

_{(Keq​)​= [C][D]/[A][B] = concentration of products over reactants (Ie Keq)}

_{note that the answer options are in terms of e… this means what is the exponent on 10^? (from log of ?)}

Question 35

what is the charge on Fe (II) or Co (II) and what do we call this phenomenon?

Answer 35

this indicates a di-cation and they both have a charge of 2+

dication: any cation, of general formula X2+, (can be denoted by X(II) formed by the removal of two electrons from a neutral species.

***if the dication is from the d block (transition metal), then the electron loss will result in changes to removal of electrons from S orbitals BEFORE d orbitals (unlike the other elements where the removal is from p first)

Question 36

if there is loss of electrons from atom of the d block, will the s or d orbitals lose electrons first?

Answer 36

the s orbitals.

(unlike the other elements where the removal is from p before s). atoms will ALWAYS lose electrons from the s orbitals before they lose any electrons from the d block

Question 37

phosphorylation occurs via kinase because it is a _______________ reaction

Answer 37

group transfer

kinase is a type of tranferase (Specific to phosphate reactions)

Question 38

what is the relationship between conjugated systems/delocalization of charge and solution color?

Answer 38

The more conjugated the system the lower the energy of light that will be absorbed and they will therefore reflect what is not absorbed. It is this reflected portion that the eye will perceive as the color of that object. A less highly conjugated system will require the absorption of the higher energy part of the spectrum, allowing the lower energy parts to be reflected to the eye. Note that the color that is reflected is the complementary color of the color that is absorbed. For example if the high energy violet portion of the spectrum is absorbed, its complementary color of yellow is what is observed.

If the lower energy blue or green colors are absorbed, the colors orange or red would be observed. For example, retinol, or vitamin A, has five conjugated double bonds and absorbs the violet part of the spectrum, thus appearing as yellow. The more highly conjugated ß-carotene, having eleven conjugated double bonds absorb in the lower energy blue and green portions of the spectrum and appear as orange and red. The 1,3,5-heptatriene, having only three conjugated double bonds does not absorb in the visible portion of the spectrum and thus appears as being colorless.

Question 39

in each variant, the substitution that took place changed the side chain at the affected position in which way?

1. increased hydrophobicity
2. decreased basicity
3. increased hydrophilicity
4. decreased steric constraints

Answer 39

D. decreased steric constraints

recall that WT means wild type and V86A means valine was replaced at position 86 by alanine.

(same goes for all of them)

Question 40

catalytic efficiency is defined by the ratio of

Answer 40

K_cat/K_m

Question 41

pic

Answer 41

Question 42

pic

Answer 42

Kcat, turnover number, is a measure of how many substrates one (1) enzyme can convert into a product per second.

Question 43

a wave represents a full 360 degrees, so the phase difference that causes destructive interference is

Answer 43

half a wave = 180 degrees

Question 44

T/F: it a molecule is not metabolized it provides no energy and therefore no calories

Answer 44

true

Question 45

T/F: when an acid and a base are present in equal concentrations the pH of the buffer equals the pka of the acid

Answer 45

true

Question 46

T/F: reaction rate always increase with temperature

Answer 46

true

*but be careful with this generalization: It doesn’t always mean more products are formed per unit time becaus it depends on whether it’s an exothermic or endothermic reaction. But it is always true that for a given direct (to reactants or towards products) the rate will increase

Question 47

Increasing the volume of a reaction vessel will reduce the concentrations of the reacting gases. In order to reestablish equilibrium, the reaction will shift to favor

Answer 47

the side that makes more moles of gas.

Question 48

how do you find the number of stereoisomers in a meso compound

Answer 48

2 (#stereocenters) - 1= total stereoisomers possible

Question 49

T/F: total torque is zero when a system is in static equilibrium

Answer 49

True

e.g. a phone poll that is getting tugged by a rope that someone is pulling form the ground the top does not have any torque

Question 50

Motion “away” always corresponds to a frequency decrease/increase?

Answer 50

decrease

Thus, if a (detector) hears/detects a frequency of 1000 Hz, the actual source frequency must be higher than 1000 Hz but not by more than 100%

Question 51

When a wave changes medium, the frequency remains constant

Answer 51

true

*if you try to use f=c/λ to solve, you will think “Oh I know.. if speed decreases, frequency also decrease” but that is NOT true. Frequency is constant

Question 52

Eº < 0 for a half reaction corresponds to a non-spontaneous/spontaneous? reaction

Answer 52

non-spontaneous

… and Eº > 0 is spontaneous

(DONT just look for the highest number when asked for the best oxidant whether or not its negatively charged)

Question 53

true in oxidative phosphorylation, each FADH2 = 2 ATP; each NADH = 1.5 ATP

Answer 53

true

Question 54

vasopressin is also known as

Answer 54

ADH

Question 55

T/F: DNA gyrase supercoils bacterial DNA which facilitates replication

Answer 55

True:

The job of DNA gyrase is to continually introduce negative supercoils into the circular bacterial genome. Then, when the helix is opened for replication and positive supercoils are introduced (the DNA gets more tightly wound at the ends of the replication fork), the already-present negative supercoils cancel out the newly introduced positive supercoils, and DNA tension is kept to a minimum

Question 56

diff between steroid and peptide hormones

Answer 56

Steroid hormones (ending in ‘-ol’ or ‘-one’) include estradiol, testosterone, aldosterone, and cortisol. They are hydrophobic and can enter into the cell

The peptide hormones are amino acid – derived (ending in ‘-ine’) are derived from tyrosine and tryptophan and include epinephrine and norepinephrine (produced by theadrenal medulla). These are hydrophilic and have to act on the cell via second messenger system

Question 57

____________is most likely level of structure of a protein that is altered during a conformational change

Answer 57

tertiary

Question 58

T/F: Less time in G2 means the cells will be smaller

Answer 58

true

Question 59

Glycogen phosphorylase catalyzes the rate-limiting step in

Answer 59

glycogenolysis

ie breaking bonds between glucose molecules