Kuwait University Chemistry Aptitude Test key terms

The calculation of the amounts of reactants and products in a chemical reaction using the mole ratios given by the balanced equation.

The amount of a substance containing Avogadro's number (6.022 × 10^23) of particles; its mass in grams equals the molar mass.

The mass in grams of one mole of a substance, found by adding the atomic masses of all atoms in its formula.

The reactant that is used up first in a reaction and therefore determines the maximum amount of product that can form.

The actual mass of product obtained divided by the theoretical mass predicted by stoichiometry, multiplied by 100.

The simplest whole-number ratio of atoms of each element in a compound, such as CH2O for glucose.

A concentration unit equal to the number of moles of solute dissolved in one litre of solution, written mol/L or M.

Adding solvent to a solution to lower its concentration; the moles of solute stay constant, so M1V1 = M2V2.

The ratio of product concentrations to reactant concentrations, each raised to its coefficient power, at equilibrium; its size indicates whether products or reactants dominate.

When a system at equilibrium is disturbed by a change in concentration, pressure, or temperature, it shifts in the direction that partly offsets the change.

A logarithmic scale from 0 to 14 measuring hydrogen ion concentration: pH = −log[H+]; values below 7 are acidic and above 7 are basic.

A substance that donates a proton (H+) to another species or accepts an electron pair; aqueous acids increase hydrogen ion concentration.

The loss of electrons by a species, shown by an increase in oxidation number; it is always paired with reduction.

The gain of electrons by a species, shown by a decrease in oxidation number; the opposite half of a redox reaction.

The equation PV = nRT relating pressure, volume, moles, and absolute temperature of a gas, where R is the gas constant.

The pressure that one gas in a mixture would exert if it alone occupied the whole container; total pressure is the sum of partial pressures.

The heat absorbed or released by a reaction at constant pressure, denoted ΔH; negative for exothermic and positive for endothermic reactions.

The minimum energy that colliding particles must possess for a reaction to occur; a catalyst lowers it without being consumed.

A substance that speeds up a reaction by providing an alternative pathway with lower activation energy, while remaining chemically unchanged overall.

The average energy required to break one mole of a particular covalent bond in the gas phase; used to estimate reaction enthalpy.

An atom of the same element with the same number of protons but a different number of neutrons, giving a different mass number.

The number of protons in the nucleus of an atom, which uniquely identifies the element and fixes its position in the periodic table.

A measure of how strongly an atom attracts the shared electrons in a chemical bond; it increases across a period and decreases down a group.

A covalent bond in which electrons are shared unequally because the two atoms differ in electronegativity, creating partial charges.

The energy needed to remove one mole of electrons from one mole of gaseous atoms or ions; it generally rises across a period.

The change in concentration of a reactant or product per unit time; it increases with temperature, surface area, concentration, and catalysts.

The instantaneous rate of change of a function with respect to its variable, defined as the limit of the difference quotient.

The value that a function approaches as its input approaches a given point, whether or not the function is defined there.

The accumulated total of a function over an interval, interpreted as the area under its curve and computed as the reverse of differentiation.

A property of a function whose graph has no breaks, jumps, or holes at a point: the limit exists and equals the function value there.

The expression x = (−b ± √(b² − 4ac)) / 2a giving the roots of the equation ax² + bx + c = 0.

The quantity b² − 4ac in a quadratic equation; its sign tells whether the roots are real and distinct, repeated, or complex.

The exponent to which a base must be raised to produce a given number; log base b of x equals y when b^y = x.

A function of the form f(x) = a·b^x, where the base b is positive and not 1; it grows or decays at a rate proportional to its value.

A quantity having both magnitude and direction, often written as components; vectors add by resolving into perpendicular directions.

A physical quantity described by magnitude alone, with no direction, such as mass, time, or temperature.

The single vector that produces the same effect as two or more vectors combined, found by vector addition.

The net force on an object equals its mass times its acceleration (F = ma); acceleration is in the direction of the net force.

A sketch showing one object in isolation with all external forces acting on it drawn as labelled arrows.

The product of an object's mass and velocity; in an isolated system the total momentum before a collision equals the total after.

The energy an object possesses due to its motion, equal to one half its mass times the square of its speed.

The energy transferred when a force moves an object through a distance, calculated as force times displacement times the cosine of the angle between them.

The current through a conductor is directly proportional to the potential difference across it and inversely proportional to its resistance (V = IR).

The opposition a material offers to the flow of electric current, measured in ohms and equal to voltage divided by current.

The number of complete oscillations passing a point each second, measured in hertz and equal to speed divided by wavelength.

The distance between two consecutive corresponding points on a wave, such as crest to crest, usually measured in metres.

A conclusion drawn from evidence and reasoning rather than stated directly; readers combine clues in a text with their own knowledge.

The central point that a paragraph or passage is built around, often stated in a topic sentence and supported by details.

Restating the meaning of a text in your own words while keeping the original sense, usually at a similar level of detail.

A word or phrase such as however, therefore, or in addition that signals the logical relationship between ideas in a text.

The grammatical rule that a verb must match its subject in number and person, so a singular subject takes a singular verb.