MCAT Content Review

113 flashcards by MentisLibrary

Original study items across all four MCAT sections: chemical and physical foundations, biological and biochemical foundations, psychological and social foundations, and critical analysis and reasoning skills.

State Newton's second law and the condition for translational equilibrium.
Net force equals mass times acceleration, $F_{net} = ma$. Translational equilibrium means the net force is zero, so velocity is constant, not necessarily zero.
What does the work-energy theorem state?
The net work done on an object equals its change in kinetic energy.
When is mechanical energy conserved?
When only conservative forces act, so no energy leaves the system as heat through friction or air resistance.
What conditions define static equilibrium for an extended body?
Both the net force and the net torque about any axis must be zero.
How does Pascal's principle apply to a hydraulic lift?
Pressure applied to an enclosed fluid is transmitted undiminished, so a small force on a small piston produces a large force on a large piston.
Write the continuity equation and say what it implies.
$A_1 v_1 = A_2 v_2$ for an incompressible fluid, so fluid speeds up where the tube narrows.
What does Bernoulli's equation say about pressure and velocity?
Along a streamline the sum of static pressure, dynamic pressure and gravitational term is constant, so faster flow means lower pressure at the same height.
How does vessel radius affect resistance to viscous flow?
Resistance is inversely proportional to the fourth power of the radius, so halving the radius multiplies resistance by sixteen.
State Archimedes' principle.
The buoyant force on a submerged object equals the weight of the fluid it displaces.
How do resistors combine in series and in parallel?
In series resistances add directly. In parallel the reciprocals add, so the total is always less than the smallest individual resistor.
What is capacitance, and how do capacitors combine?
Capacitance is charge stored per unit voltage, $C = Q/V$. Capacitors add directly in parallel and reciprocally in series, the opposite of resistors.
Galvanic vs electrolytic cell: which is spontaneous, and where does oxidation occur?
A galvanic cell is spontaneous with a positive cell potential and a negative free energy change. An electrolytic cell requires an external power source. Oxidation occurs at the anode in both.
What is the Doppler effect for sound?
The observed frequency rises as source and observer approach and falls as they separate, because the wavefronts are compressed or stretched.
Write the thin lens equation and the sign convention for a converging lens.
$1/f = 1/o + 1/i$, with focal length positive for a converging lens and negative for a diverging lens. A positive image distance means a real, inverted image.
Compare alpha, beta and gamma decay in terms of the nucleus.
Alpha decay emits a helium nucleus, reducing mass number by 4 and atomic number by 2. Beta minus decay converts a neutron to a proton and raises atomic number by 1. Gamma decay releases energy without changing either number.
What does the photoelectric effect demonstrate?
That light behaves as discrete quanta. Electrons are ejected only when photon energy exceeds the work function, and the maximum kinetic energy is the photon energy minus the work function.
Write the Henderson-Hasselbalch equation and say when a buffer is strongest.
$pH = pK_a + \log([A^-]/[HA])$. A buffer resists change best when the pH equals the pKa, where the conjugate pair concentrations are equal.
What does the solubility product constant describe?
The equilibrium between an ionic solid and its dissolved ions. A larger Ksp means greater solubility for salts of the same stoichiometry.
What happens at the half-equivalence point of a weak acid titration?
Half the acid has been converted to conjugate base, so the concentrations are equal and the pH equals the pKa.
Rank the intermolecular forces from strongest to weakest.
Ion-dipole, then hydrogen bonding, then dipole-dipole, then London dispersion forces.
Summarize the periodic trends in electronegativity, ionization energy and atomic radius.
Electronegativity and ionization energy increase up and to the right. Atomic radius increases down and to the left.
Relate hybridization to molecular geometry.
An sp3 center is tetrahedral at about 109.5 degrees, sp2 is trigonal planar at 120 degrees, and sp is linear at 180 degrees.
What does Le Chatelier's principle predict?
A system at equilibrium shifts to partially oppose an applied change in concentration, pressure or temperature.
Write the Gibbs free energy equation and state what makes a reaction spontaneous.
$\Delta G = \Delta H - T\Delta S$. A reaction is spontaneous when the free energy change is negative.
How does a catalyst change a reaction?
It lowers the activation energy by providing an alternative pathway, speeding both the forward and reverse reactions equally.
How is a rate law determined?
Experimentally, by measuring how the rate responds to changes in each reactant concentration. It cannot be read off the balanced equation.
Which properties of a solution are colligative?
Boiling point elevation, freezing point depression, vapor pressure lowering and osmotic pressure.
How does thin layer chromatography separate compounds?
By differential affinity between a polar stationary phase, usually silica, and a less polar mobile phase. Less polar compounds travel farther and have a higher retention factor.
How does an acid-base extraction separate an amine from a neutral compound?
Adding aqueous acid protonates the amine, making it charged and water soluble, so it moves into the aqueous layer while the neutral compound stays in the organic layer.
When do real gases deviate most from ideal behavior?
At high pressure and low temperature, where molecular volume and intermolecular attractions are no longer negligible.