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National MDCAT Chemistry Flashcards
60 question-and-answer cards covering Chemistry as it is examined in National MDCAT. 24 of them are printed below, taken from across the deck — no signup, no paywall on the preview.
24 sample cards from the Chemistry deck
Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.
Define the boiling point of a liquid in terms of vapour pressure.
The boiling point is the temperature at which the vapour pressure of the liquid becomes equal to the external (atmospheric) pressure.
What is viscosity, and how does it generally change with temperature for liquids?
Viscosity is the resistance of a liquid to flow, caused by internal friction between layers. For liquids, viscosity decreases as temperature increases.
What is the difference between crystalline and amorphous solids?
Crystalline solids have a regular, long-range ordered arrangement of particles, sharp melting points, and are anisotropic. Amorphous solids have a disordered (short-range) arrangement, melt over a range, and are isotropic (e.g., glass).
List the four main types of crystalline solids based on the particles and bonding.
Ionic solids (ions, electrostatic bonds), covalent/network solids (atoms, covalent bonds), molecular solids (molecules, van der Waals/H-bonds), and metallic solids (cations in a sea of electrons).
Compare the melting points and electrical conductivity of ionic, covalent, molecular, and metallic solids.
Ionic: high m.p., conduct only when molten/dissolved. Covalent network: very high m.p., usually non-conducting (except graphite). Molecular: low m.p., non-conducting. Metallic: variable m.p., conduct in solid and molten states.
What is a crystal lattice and a unit cell?
A crystal lattice is the regular, repeating three-dimensional arrangement of particles in a crystal. The unit cell is the smallest repeating unit that, when repeated in all directions, generates the entire lattice.
Define isomorphism and polymorphism with respect to crystals.
Isomorphism: different substances having the same crystalline form/shape (e.g., due to similar formulae). Polymorphism: the same substance existing in two or more distinct crystalline forms (e.g., diamond and graphite for carbon).
Write the expression for the equilibrium constant Kc for the reaction aA + bB <-> cC + dD.
Kc = ([C]^c [D]^d) / ([A]^a [B]^b), where concentrations are the equilibrium molar concentrations.
What does a very large value of K and a very small value of K tell you about a reaction at equilibrium?
A large K means products are favoured (reaction goes nearly to completion); a small K means reactants are favoured (very little product forms at equilibrium).
State Le Chatelier's principle.
If a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the equilibrium shifts in the direction that tends to counteract (oppose) that change.
How does increasing pressure affect a gaseous equilibrium according to Le Chatelier's principle?
Increasing pressure (decreasing volume) shifts the equilibrium toward the side with the fewer moles of gas; if both sides have equal moles of gas, pressure has no effect on the position of equilibrium.
In the Haber process (N2 + 3H2 <-> 2NH3, exothermic), what conditions favour maximum yield of ammonia, and why are compromise conditions used?
High pressure and low temperature favour ammonia yield (fewer gas moles and exothermic). In practice moderate temperature (about 450 C), high pressure (about 200 atm), and an iron catalyst are used as a compromise to achieve a reasonable rate and yield.
Define the rate of a chemical reaction.
The rate of a reaction is the change in concentration of a reactant or product per unit time (e.g., mol dm^-3 s^-1).
What is the difference between average rate and instantaneous rate of reaction?
Average rate is the change in concentration over a measurable time interval; instantaneous rate is the rate at a particular instant, obtained from the slope of the tangent to the concentration-time curve at that point.
Write the general form of a rate law and define the order of reaction.
Rate = k[A]^m[B]^n, where k is the rate constant. The order with respect to a reactant is its exponent (m or n); the overall order is the sum (m + n). Orders are determined experimentally, not from the balanced equation.
State the Arrhenius equation and explain how activation energy and temperature affect the rate constant.
k = A e^(-Ea/RT), where A is the frequency factor and Ea is the activation energy. A higher temperature or a lower Ea gives a larger rate constant k and thus a faster reaction.
List the main factors that affect the rate of a chemical reaction.
Nature of reactants, concentration (or pressure for gases), temperature, surface area of solids, presence of a catalyst, and (for some reactions) light/radiation.
How does a catalyst increase the rate of a reaction?
A catalyst provides an alternative reaction pathway with a lower activation energy, allowing more molecules to react successfully, without being consumed and without changing the position of equilibrium.
Define internal energy (E or U) of a system.
Internal energy is the total energy (kinetic + potential) of all the particles in a system. Its absolute value cannot be measured; only the change (delta E) is determined.
Define enthalpy (H) and write the relationship between enthalpy change and internal energy change.
Enthalpy H = E + PV is the heat content of a system at constant pressure. The change is delta H = delta E + P delta V; delta H equals the heat absorbed or released at constant pressure (q_p).
What is the sign convention of delta H for exothermic and endothermic reactions?
Exothermic reactions release heat and have delta H negative; endothermic reactions absorb heat and have delta H positive.
State the first law of thermodynamics and its mathematical form.
Energy can neither be created nor destroyed, only converted from one form to another. delta E = q + w, where q is heat added to the system and w is work done on the system.
State Hess's law of constant heat summation.
The total enthalpy change for a reaction is the same whether it occurs in one step or several steps, depending only on the initial and final states and not on the pathway taken.
How is Hess's law used to calculate an unknown enthalpy change?
By adding or subtracting the enthalpy changes of known reactions (manipulating equations and their delta H values, reversing signs when an equation is reversed) so they sum to the target reaction, since delta H is a state function.
What this deck covers
The Chemistry deck follows the National MDCAT Chemistry syllabus — 18 chapters and 54 topics — so questions land on material that is genuinely examinable rather than trivia around it. That works out to roughly 3.3 cards per chapter.
Answers are written to be recallable, not just readable — averaging about 185 characters, which is long enough to carry the reasoning and short enough to say out loud.
A deck like this earns its keep on the second and third pass. Read the syllabus first so you know the shape of the subject, then use the cards to find the specific facts that have not stuck.
Chemistry flashcards FAQ
How many Chemistry flashcards are in this National MDCAT deck?
60 cards. This page previews 24 of them, sampled evenly across the deck so you can judge the difficulty before installing anything.
Are these National MDCAT flashcards free?
Yes. The preview here is free to read with no signup, and the full 60-card deck is free inside the Examius app.
What do the Chemistry cards cover?
They follow the National MDCAT Chemistry syllabus — 18 chapters and 54 topics — so the questions track what is actually examinable.
How should I use these flashcards?
Read the syllabus first so you know the shape of the subject, then drill the deck. Examius schedules each card with spaced repetition, so cards you keep missing come back sooner and ones you know drift further apart.