MCAT General Chemistry Study Questions
These are questions I came up with when I was studying for the MCAT.
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Atoms and Molecules
- What are the components of an atom? What parts of an atom contribute
significantly to the atomic weight?
- What would the mass of a mole of neutrons?
- What are orbitals? How many electrons can an orbital hold?
- What are the four different quantum numbers? What is a synonym for
the azimuthal quantum number?
- What does the term AUFBAU refer to? What is Hund's rule? What
is the Pauli exclusion principle?
- Which will fill up first, 4s or 3d? Using the periodic table, what
is the general pattern for the filling of orbitals?
- Where on the periodic table is the s-block? the p-block? the
d-block? the f-block? Which block are the transition metals
- What are the alkali metals? What are the alkaline earth metals?
- What are the halogens? What are the noble gases?
- Which elements are found naturally in a diatomic form?
- Why are noble gases so inert?
- What two electronic conditions does a nucleus seek? Which condition
is left unsatisfied in radicals? Which condition is left unsatisfied in
- What is the term for two or more atoms connected by a covalent bond?
- What on the periodic table is meant by the term FAMILY? What about
GROUP? What about PERIOD?
- What is "energy of ionization"? What side of the periodic table has
elements with low energies of ionization? What does this mean?
- What is meant by "electron affinity"? How does electron affinity
tend to change going left to right and going top to bottom?
- Why, along a period, does the atomic radius tend to get smaller?
Among a cation, a noble gas, and an anion with the same electronic
configuration, which has the larger radius? What happens to the radius
as one goes from top to bottom on the periodic table?
- What is meant by "effective nuclear charge"? What is shielding?
- What is meant by "quantized" energy levels?
- What is an electronic transition? What happens as an electron goes
from a lower level to a higher level? What happens in the reverse?
What is meant by "exited state"? What is the "ground" state?
- What does an s orbital look like (conceptually, at least)? How many
s orbitals are found on a shell? What do p orbitals look like?
What shell is the first to have p orbitals? How many are there on that
- When drawing orbitals, what do the positive and the negative signs on the
orbital lobes indicate? Better, what DON'T they indicate?
- What are valence electrons? How many electrons does it take to fill
hydrogen's valence shell? How many to fill oxygen's valence shell?
- How many electrons are represented in the symbol for a single bond?
- In what shell is the first d orbital found?
- What is the formula for the energy of a photon?
- What is the difference between an ionic bond and a covalent bond?
What is an unevenly balanced covalent bond called?
- Besides conjugated organic molecules, what type of atoms/molecules
commonly contribute to the colors we see (by absorbing light)?
- What is the difference between a solution and a colloid? Which will
scatter a light beam? What is this phenomenon called?
- What is meant when a compound "precipitates"? What is meant when a
solution is "saturated"? What is the common-ion effect?
- What is the difference between molarity and molality? What are the
units of each? Which is volume dependent? Which is temperature
dependent? Is volume dependent on temperature?
- What is molar solubility? What is Ksp? What is the difference
between the two? How do you convert between the two? What is meant by
- What do high solubility products indicate? What do low values
- Which is the larger number : 3 x 10-6 or 3 x 10-10?
(common absent-minded mistake)
- What can be said about the solubility of Na+, K+,
and NH4+ ionic compounds? What can be said about
the solubility of ionic compounds containing nitrate?
- If solubility is a relative concept, then around what value is considered
the borderline between "soluble" and "insoluble"? What is meant by
- Which is more water soluble : NaOH or Mg(OH)2? What can
be done to the solution to make the least soluble compound more soluble?
- What is meant by miscible? Can certain gases be non-miscible?
Can certain liquids be non-miscible?
- How does the equilibrium relate to the rates of the reactions? Does
changing the activation energy of a reaction change the equilibrium? Why
or why not?
- What is Le Chatelier's principle? What does it predict?
- What is the general expression for a reaction's equilibrium constant?
Is the same constant used with different temperatures? Is the same
constant used with different reactant/product concentrations?
- Adding more product to a reaction at equilibrium will shift the reaction
which way? Adding more product?
- What is meant by "Reaction Quotient"? Under what conditions does the
Qc=Kc? When Qc<Kc, which way will the reaction proceed?
- If a reaction is endothermic, will the equilibrium constant be lower or
higher at a higher temperature? What about for exothermic reactions?
- What is the difference between the constants Kc and Kp? How are the
amounts of the reactants/products expressed in each of the constants?
For a given reaction of a gases, are the Kp and Kc different values? Why
or why not?
- For a reaction of gases in equilibrium, will adding an inert gas to the
container shift the equilibrium? Will this inert gas affect the partial
pressures of the gases involved in the reaction? Will decreasing the
volume shift the equilibrium? Will decreasing the volume affect the
partial pressures of the gases involved in the reaction?
- What types of reaction participants are excluded in the equilibrium
expression? Are pure gases included? Are pure liquids? Are
pure solids? Are impure solids?
- Must a reaction's equilibrium expression be determined only by experiment?
- In an equilibrium expression, what is on top: reactants or products?
- If 2 moles of compound X react with 1 mole of compound Y to form compound
Z, what is the equilibrium expression?
- What is meant by a reaction "proceeding to completion"? How can
reactions be encouraged to do so?
- What is the molarity of water? Is this ever included in equilibrium
- What is meant by vapor pressure? Does a liquid with a high vapor
pressure have a high or low boiling point?
- What happens to a liquid's vapor pressure as the temperature increases?
- What is the temperature referred to at which a liquid's vapor pressure
equals atmospheric pressure?
- What happens when a liquid's vapor pressure is higher than the liquid's
vapor phase partial pressure but lower than atmospheric pressure?
- When water is at room temperature at sea level, is the water's vapor
pressure above or below atmospheric pressure?
- Does it take longer to boil an egg at higher altitude or a lower altitude?
Why? Does water at a high altitude boil at a lower or higher temperature
than water at sea level?
- Suppose a closed container is half full of liquid... what is the pressure
of the gas above the liquid equal to? What would happen to the pressure
if the volume above the liquid was halved? What would happen to the
pressure if more pure liquid is added?
- What is meant by "dynamic equilibrium"?
- Do solids have vapor pressures?
- What is a phase? What is meant by an aqueous phase? What is
meant by an organic phase?
- What does the term "fusion" (not the nuclear type) mean?
- Is melting endothermic or exothermic? When is melting spontaneous?
When is melting non-spontaneous?
- What is meant by the term "heat capacity"? What is meant by
"specific heat capacity"? What is the specific heat capacity of water?
How does the heat capacity of water compare to other materials?
- How many joules are in one calorie? How many calories are in one
- What is the "heat of vaporization"? What is the "heat of fusion"?
- At normal atmospheric pressure, what is the temperature of ice water in
equilibrium? What would happen to the temperature if heat were added?
Why? What would happen if heat (thermal energy) were taken away?
- Under normal conditions, why can't you heat boiling water above 100
degrees C? What happens to the water when more heat is added?
- Where on a P vs. T graph is the triple point? The critical point?
Where on a P vs. V graph is the critical pressure?
- How does the mass of 1 mol of liquid water molecules in liquid form
compare to that in ice form? How does the volume compare? How does
the density compare?
- Why is the solid form of water unusual? What does the slope of the
solid-liquid line in a P vs. T graph of water look like? That of other
- What is meant by the term "specific gravity"? What is the density of
water in SI units? If something has a specific gravity of 17, what is
- What happens to the energy invested in melting a solid? What happens
to the energy used to vaporize a gas? Why doesn't the temperature
- What is an ideal gas? What is a real gas? How do they differ?
Under what conditions does a real gas approximate an ideal gas? (temperature?
- What is the ideal gas formula?
- What does Boyle's law say? What does Charles law say?
- What is Avogadro's law say?
- What is meant by partial pressure?
- What many torr is atmospheric pressure? bar? Pa? atm?
mmHg? What is the relationship between bars and pascals? What is
the relationship between mmHg and torr? Which is the SI unit?
- What is the difference between absolute pressure and gauge pressure?
Which one can be negative? How?
- What effect does temperature generally have on the solubility of a gas in
a liquid? How is this different than a solid in a liquid?
- How many liters will one mole of gas molecules take up at STP? <memorize
- What are the main components of air?
- What is the weight of the air in the atmosphere over an area of one square
- What are the four main colligative properties? Are the properties of
these solutions changed by the amount of substance present? Are they
changed by the nature of the substance present?
- What does dissolving salt in water do to its melting point? to its
boiling point? Will a fresh water freeze before salt water? Will
fresh water boil before salt water?
- What constant is used to calculate the change in the freezing point?
What are its units?
- What is the approximate mass of water in a liter of aqueous solution?
- What does hyperosmolar refer to? What is meant by hypoosmolar?
What type of membrane must be present to observe osmosis?
- Suppose a membrane permeable to most ions separates two compartments of
water. When salt is added to one compartment, what will happen? Is
- Suppose a membrane that is permeable to only water separates two
compartments of water. When salt is added to one compartment, what is
observed? Is this osmosis?
- What effect does dissolved non-volatile solutes have on the vapor pressure
of a liquid?
- What is the procedure for using freezing-point depression to determine the
molecular weight of a substance?
- What is meant by van't Hoff factor? Ideally, what would that be for
sodium chloride? How about that for calcium chloride?
- What distinctions must be made between the equilibrium of a reaction and
the rate at which the reaction takes place? How are these two concepts
- What is the activation of energy of a reaction? What two values are
subtracted? How is this different from the free energy change of a
reaction? Which two values are subtracted for this?
- How does a catalyst change the rate of a reaction? Does it change
the rate of the reverse reaction? How does a catalyst affect the
- Must a real reaction's rate constant expression be determined only by
- What is meant by ELEMENTARY reaction? How is this treated
differently than a multi-step reaction? How is the rate expression
determined for an elementary reaction?
- For a multi-step reaction in which all the individual reactions are known,
which step will decide the expression for the rate constant?
- When a slow elementary step is preceded by a fast reaction, how are the
reactant concentrations for the slow step approximated?
- What is being measured by the value "reaction rate"? Is the rate of
a reaction affected by the concentrations of the products or reactants?
- The reaction rate is equal to the rate expression multiplied by what?
- What happens when the rate of the forward reaction equals the rate of the
reverse reaction? At this point, what is the overall rate of the
- What is meant by "reaction order"? For a real life reaction, how
must this reaction order be determined?
- What is a zero-order reaction? Does the rate of the reaction change
as the reaction proceeds? What is a first order reaction? Does the
rate of the reaction change as the reaction proceeds?
- What is the order of a reaction that decays with a constant half life?
How many half lives will it take for a reactant to fall to below 13% of its
- Why do kinetics experiments often measure only the first part of a
- Assuming none of the reactants or products decay with increased
temperature, how do higher temperatures affect the rate of a reaction?
Why? How does temperature affect equilibrium constants?
- When reacting compounds X and Y to form Z, what is suggested when the rate
of Z formation doubles when the concentration of X is doubled? If the
rate increases 9 fold when the concentration of Y is tripled, what is the
order of Y? What is the overall reaction order?
- Why are high temperatures often used to determine what the thermodynamic
properties of a reaction are?
- What is the difference between the reaction constants k and K?
- Is HCl a molecule or an ionic compound? What about NaOH? Is it
possible to have a covalent compound in solid form that ionizes upon addition
- What is an acidity constant? How is this abbreviated? What is
a pKa? What type of acid is indicated by a low acidity constant? a
- What is the equilibrium expression for Ka? What is the equilibrium
expression for Kb?
- What is Kw? What is the value for pKw? Does this change with
temperature? Does this equilibrium always hold?
- What is meant by amphoteric? Does an amphoteric acid have a
conjugate base? Does a non-amphoteric have a conjugate base?
- Water is amphoteric. If you know the pKa for water, 14 -
pKa represents the pKb for what molecule? What would you
guess is a common mistake that students make in regards to what molecule the
pKb for an amphoteric acid/base refers to?
- What is the conjugate acid of water? What is the conjugate base of
water? What is the pKa of water? (not as easy as you may think)
- How do you convert from pKa to Ka? How do you convert from Ka to pKa?
8.0 x 10-3 would be within what pKa range (by quick estimate)?
- How do you calculate the Kb of the conjugate base from the Ka? What
about the pKb of the conjugate base from the pKa?
- What does pH measure? How is this concentration value converted into
pH? How is pH converted into this concentration value?
- What is pOH? How is is calculated from pH?
- What is the difference between pH and pKa? What about pOH and pKb?
- How does one derive the Henderson-Hasselbach equation from pH and pKa?
(derive it yourself)
- Which definition of acids and bases is the most generic? Which is
the most specific for aqueous solutions?
- What is the pH when 10-12 mols of HCl are added to 1 liter of
water? Why isn't this value 12? What must not be ignored when
adding amounts of acid this small that can be ignored when adding a large
amount of strong acid? (common trap)
- Suppose you have a liter of water... what is the [H+] after about 500 mL
of 0.1 M HCl has been added? Why isn't it 0.05? What must not be
forgotten when mixing two aqueous solutions together? (common trap, esp. in
- What is the end point of titration? What is the equivalence point?
What is the difference?
- What does the slope of the line at the equivalence point in a titration
graph look like? What about the slope of the line at the pKa?
- What is the concentration of an acid compared to its conjugate base when
- What are buffers? What is the relationship between the two
components in a buffer? What are their relative concentrations when the
buffer is at its maximum capacity? Why don't strong acids or strong
bases work as buffers? What does the titration graph look like as it
progresses through a buffered region?
- In aqueous solution, what makes an acid strong? Is H20 a
stronger acid than HCl? Is H30+ a stronger acid
than HCl? Is H20 a stronger acid than acetic acid? Is H30+
a stronger acid than acetic acid?
- In aqueous solution, what makes an base strong? Is H20 a
stronger base than NH3? Is OH- a stronger base
than NH3? Is H30+ a
stronger acid than NH4+?
- At what point does water "level" the strength of an acid? Is HCl in
aqueous solution stronger than other strong acids? What type of solvent
would allow fewer acids to be considered "strong"?
- Which of the following is the strongest acid : HF, HCl, HBr, or HI?
Which is a weak acid in aqueous solution? Which has the strongest
- When a strong base is titrated with a strong acid, what is the pH of the
equivalence point? Which would have an equivalence point with pH < 7 : a
strong acid + weak base OR a weak acid + strong base?
- When titrating with a strong acid, does a weak base require more acid than
a strong base? (common trap)
- How does ammonia increase the concentration of hydroxide ions when added
- Is ammonia commonly considered an acid or base? How about ammonium?
Which has a lone pair of electrons?
- What approximations can sometimes be made when calculating the pH of a
- What are indicators? Where in a titration graph would the best
indicator's range be located?
- What is thermodynamics? Does thermodynamics predict whether a
reaction will occur spontaneously? Does it predict how fast that
reaction will reach equilibrium? Does it predict what that equilibrium
- What is the first law of thermodynamics? A machine that violated
this would be able to do what?
- What is the second law of thermodynamics? A machine that violated
this would be able to do what?
- What is meant by "spontaneous"? What value measures the spontaneity
of a reaction? (do not say enthalpy) Is this value positive or
negative for a spontaneous reaction?
- What does entropy measure? What type of entropy change (positive or
negative) contributes to a reaction being spontaneous?
- What does enthalpy measure? What type of enthalpy change contributes
to a reaction being spontaneous?
- What is "enthalpy of formation"? How can this be used to determine
the heats of reaction? What is the enthalpy of formation of oxygen gas?
- What is the formula for Gibb's Free Energy? What are the two main
components for determining ΔG? Which
should each be to contribute to a more negative value for ΔG?
- What effect will a catalyst have on ΔG?
- Assuming ΔH and ΔS are
constant over a range of temperatures, which of these components has its
effect on ΔG modified by temperature?
- Reactions with negative ΔH values are
called what? What about positive ΔH
- Increasing the temperature of a reaction with a negative change in entropy
will ideally do what to the spontaneity of the reaction? What about a
reaction with a positive change in entropy?
- What type of change in entropy can be expected for reactions in which a
solid becomes a liquid? For reactions in which a liquid becomes a solid?
For a reaction in which two moles of gas react to form three moles of gas?
- What can be said about the spontaneity of reaction with a negative
change in enthalpy and a positive change in entropy? Can a reaction be
endothermic and still be spontaneous? Is so, how? If not, why not?
- For what conditions is ΔH defined? What
conditions must exist for ΔG to be calculated?
What about for ΔG to be meaningful?
- What is the ΔG of a reaction at equilibrium?
- What is the kinetic theory of gases? What does temperature represent
in a gas?
- What term is used to denote the velocity of gas molecules which would
correspond to the average kinetic energy of the gas molecules? How might
this be different from simply the average velocity?
- Doubling the velocity of gas molecules will do what to the temperature of
- What are the conditions in STP? How does this differ from the
conditions at which most thermodynamic values are cited?
- Without doing any calculations, what is the volume (in liters) of 1 mol of
an ideal gas at STP? (memorize)
- What is a heat engine? What must exist in order for a heat engine to
- How is the efficiency of a heat engine calculated? What does an
efficiency of 1 mean? What law of thermodynamics would this violate?
- How is the change in entropy calculated? What is the
ΔS for 40 J of energy leaving a heat reservoir at
- What is the difference between ΔG and
ΔG° is cited for 25° C, under
what conditions would ΔG= ΔG°?
- What is the formula for determining ΔG of
reaction from the known ΔG° at
that temperature and the concentrations of the reactants and products?
- What is meant by internal energy? Is potential
energy part of internal energy? Is organized kinetic energy part of
internal energy? Is disorganized kinetic energy part of internal energy?
Are molecular vibrations part of internal energy?
- What does adiabatic mean? What is the difference
between the terms ADIABATIC and ISOTHERMAL? For an adiabatic process, an
increase in internal energy must be attributed to what form of energy input?
- What is an isothermal process? In this type of process,
what happens to the energy provided by work on a gas?
- What is PV work? Can a process at constant
pressure perform PV work? Can a process at constant volume perform PV
- In a constant-V process, what happens to the energy
transferred to a system as heat? In a constant-P process, what happens
to the energy transferred to the system as heat? Assuming the same
amount of heat was transferred, which system will have a higher internal
energy? What value represents the change in internal energy plus the
work performed by the system?
- If the number of moles and the temperature of an ideal
gas were held the same, what would the P versus V graph look like? How
would the graph look if plotted for a different constant temperature?
What are isotherms? On a P-V graph, what shape are isotherms of an ideal
- What is occurs when the state of a gas is taken from a
point on a P-V graph to one further to the right? What about from the
right to the left? For an isothermal process, what can be assumed about
the heat input as the state moves to a point further on the right? For
an adiabatic process, what is known about the heat input for the same change
in volume? Which will have the lower pressure (y-axis): the result of
the isothermal process or of the adiabatic process?
- In a P-V graph, what is represented by the area
encompassed by the lines in a cyclic process?
- What is a state function? Is entropy a state
function? Is internal energy a state function? Is heat a state
function? Is work a state function? Is enthalpy a state function?
Why or why not?
- The combustion of a physical chemistry textbook is
spontaneous... why is it still on my bookshelf? Why don't some
spontaneous reactions proceed?
- If there is no working air conditioner on a hot day,
would keeping the door to the refrigerator open be a good way in the long term
to cool down the room?
- What is reduction? What is oxidation?
- What unit measures a compounds desire to undergo either
a reduction or oxidation?
- What happens to the oxidizing agents in a reaction?
- What are reduction potentials? How are they
measured? What are they relative to? What does a positive value
- How does one obtain an oxidation potential given the
value of the reduction potential?
- How does one calculate the standard potential for a
reaction? Are reduction potentials affected by stoichiometry?
- How is the E of a redox reaction calculated from its
E°? What are the concentrations of the products and reactants during a
standard reaction? How is ΔG calculated from the
- In the equation ΔG = -nFE, what does F
represent? What value represents "moles of electrons"? What is the
sign of the change in free energy when E is positive?
- What is an electrochemical cell? What are the two main types?
- What electrode is defined as the one where oxidation occurs?
- What electrode is defined as the one where reduction occurs?
- What electrode is positive in a voltaic cell? Which is positive in
an electrolytic cell?
- Which type of cell requires an input of energy? Which type of cell
- What type of half reaction occurs when a metal is converted into a cation?
- What occurs when iron rusts? What happens to the oxidation number on
the iron atom? What are three common forms (oxidation states) of the
- What type of half reaction is occurring when atoms in solution deposit on
the electrode to form a solid?
- When performing electrophoresis, do anions migrate towards the anode or
the cathode? What type of cell can this be considered? Is an
outside source of electricity required?
- How can a reaction that has the same type of atoms in equal amounts on
both sides still be unbalanced?
- What is the purpose of a salt bridge? What would happen in a voltaic
cell if a salt bridge (or equivalent) were not present? Which half cell
would become more positive? Which half cell would become more negative?
- Can a cell with the standard potential of zero still produce a current?
What is a concentration cell?
- What is a "sacrificial anode"? How does this protect certain metal?
- Why does elemental sodium react violently with water? What gas is
produced in this reaction? What happens to the pH of the water?
- What is the photoelectric effect? What is the work function?
What when the energy of a photon is below that of the work function?
What happens to the extra energy when photon energy is above the work
- Does increasing the intensity of incident light cause electrons of higher
energy to be ejected? Why or why not?
- What is alpha radiation? Beta radiation?
Gamma radiation? Which type is electromagnetic in nature? Which
types have particles with mass? Which types have particles with
significant mass? Which types have charged particles?
- Alpha radiation particles can be thought of as nuclei
of what atom?
- Which type of radiation can penetrate the deepest?
- What is the difference between atomic number and atomic
mass? Which number is the superscript and which is the subscript?
Which one determines the element? For a given element, which number will
determine the isotope?
- For carbon-12, what does the number 12 represent?
- What is the mass number of an alpha radiation particle?
What is the atomic number of an alpha radiation particle?
- What type of elements tend to emit alpha radiation?
Where on the periodic table are they?
- When an atom loses an alpha particle, what happens to
the mass number? What happens to the atomic number? Is this atom a
- What is emitted when a proton converts to a neutron?
What does this conversion do to the atomic number of the atom? What does
it do to the mass number?
- What is emitted when a neutron converts to a proton?
What does this conversion do to the atomic number of the atom? What does
it do to the mass number?
- What is a positron? What is it analogous to?
- What is nuclear fission? What type of elements
tend to undergo fission (as opposed to fusion)? What is nuclear fusion?
What types of elements undergo fusion?
- What does "critical mass" refer to? How was an
element of critical mass produced in the first atomic bomb dropped on Japan?
- How might gas molecules containing isotopes of an
element be purified to increase the percentage of one of the isotopes?
- What is the name for a hydrogen atom with a neutron?
With two neutrons?
- What does iron represent in terms of nuclear stability?
- Where in the electromagnetic spectrum are gamma rays
- What is the reaction order for nuclear decay?
- What is meant by the term fissile? What about
- What does the equation E=mc2 mean?
What does each symbol in the equation represent? What units?
- What are the four fundamental forces? What keeps
the nucleus together? What force acts against the nucleus?
- Why might the mass of a nucleus differ from the sum of
the masses of the individual components? What is binding energy?
How does this relate to nuclear fusion?