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HEC USAT Chemistry Flashcards
50 question-and-answer cards covering Chemistry as it is examined in HEC USAT. 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.
What is the molecular geometry and bond angle of a molecule with four bonding pairs and no lone pairs (e.g., CH₄)?
Tetrahedral, with bond angles of about 109.5°.
What is the shape and bond angle of water (H₂O), which has two bonding pairs and two lone pairs?
Bent (angular), with a bond angle of about 104.5°.
What is the molecular shape and bond angle of ammonia (NH₃)?
Trigonal pyramidal, with a bond angle of about 107°.
What is the molecular geometry of a molecule with three bonding pairs and no lone pairs (e.g., BF₃)?
Trigonal planar, with bond angles of 120°.
List the three main types of intermolecular forces from weakest to strongest.
London dispersion forces, dipole–dipole forces, and hydrogen bonding.
What conditions are required for hydrogen bonding to occur?
Hydrogen must be bonded directly to a highly electronegative atom (N, O, or F) and interact with a lone pair on another N, O, or F.
What are London dispersion forces and what increases their strength?
Weak attractions from temporary instantaneous dipoles; their strength increases with the number of electrons (larger molar mass / surface area).
State Boyle's law.
At constant temperature and amount of gas, the volume of a gas is inversely proportional to its pressure (PV = constant).
State Charles's law.
At constant pressure, the volume of a gas is directly proportional to its absolute (Kelvin) temperature (V/T = constant).
Write the ideal gas equation and identify each term.
PV = nRT, where P = pressure, V = volume, n = moles, R = gas constant, T = absolute temperature.
State Avogadro's law.
At the same temperature and pressure, equal volumes of all gases contain equal numbers of molecules (V ∝ n).
State Dalton's law of partial pressures.
The total pressure of a mixture of non-reacting gases equals the sum of the partial pressures of the individual gases.
What molar volume does one mole of an ideal gas occupy at STP?
22.4 litres at standard temperature and pressure (0 °C, 1 atm).
What is surface tension in a liquid and what causes it?
The tendency of a liquid surface to minimize its area, caused by unbalanced intermolecular attractive forces at the surface.
What is the difference between crystalline and amorphous solids?
Crystalline solids have a regular, repeating long-range ordered arrangement of particles; amorphous solids lack long-range order.
Define vapor pressure of a liquid.
The pressure exerted by a vapor in equilibrium with its liquid at a given temperature.
At what point does a liquid boil in terms of vapor pressure?
When its vapor pressure equals the external (atmospheric) pressure.
Name the phase change from solid directly to gas, and the reverse change.
Sublimation (solid to gas) and deposition (gas to solid).
Name the phase changes: solid to liquid, liquid to gas, and gas to liquid.
Melting (fusion), vaporization (evaporation/boiling), and condensation respectively.
What is a mole and how many particles does it contain (Avogadro's number)?
The amount of substance containing 6.022 × 10²³ particles (atoms, molecules, or ions).
How do you calculate the number of moles from a given mass of a substance?
Moles = mass (g) ÷ molar mass (g/mol).
What is a limiting reagent in a chemical reaction?
The reactant that is completely consumed first, limiting the amount of product formed.
State Le Chatelier's principle.
If a system at equilibrium is disturbed by a change in concentration, pressure, or temperature, the equilibrium shifts to counteract the change.
What does a negative enthalpy change (ΔH < 0) indicate about a reaction?
The reaction is exothermic, releasing heat to the surroundings.
What this deck covers
The Chemistry deck follows the HEC USAT Chemistry syllabus — 6 chapters and 19 topics — so questions land on material that is genuinely examinable rather than trivia around it. That works out to roughly 8.3 cards per chapter.
Answers are written to be recallable, not just readable — averaging about 89 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 HEC USAT deck?
50 cards. This page previews 24 of them, sampled evenly across the deck so you can judge the difficulty before installing anything.
Are these HEC USAT flashcards free?
Yes. The preview here is free to read with no signup, and the full 50-card deck is free inside the Examius app.
What do the Chemistry cards cover?
They follow the HEC USAT Chemistry syllabus — 6 chapters and 19 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.