Gases and the Kinetic-Molecular Theory

This flashcard set covers the fundamental concepts of gas behavior, the descriptive gas laws (Boyle, Charles, Amontons, Avogadro), the Ideal Gas Law, partial pressures, stoichiometry of gases, and the Kinetic-Molecular Theory.

Pascal (Pa)

The S.I. unit of pressure, where $1\,Pa = 1\,N/m^2$.

Atmosphere (atm)

A unit of pressure defined as $101.325\,kPa$, or exactly $760\,torr$.

Barometer

A device used to measure atmospheric pressure, often using a column of mercury.

Manometer

An instrument used to measure the pressure of a gas in a laboratory experiment, categorized into closed-end and open-end types.

Boyle’s Law

The law stating that at constant temperature, the volume occupied by a definite mass of gas is inversely proportional to the applied pressure ($PV = K$).

Charles’s Law

The law stating that the volume of a gas sample varies directly with its absolute temperature if the pressure is held constant ($\frac{V}{T} = K$).

Absolute Zero

The theoretical temperature at which a gas would have zero volume, corresponding to $-273.15^{\circ}C$ or $0\,K$.

Amontons’s Law

The gas law stating that pressure is directly proportional to absolute temperature when volume and amount of gas are held constant ($\frac{P}{T} = K$).

Standard Molar Volume

The volume occupied by $1\,mol$ of an ideal gas at Standard Temperature and Pressure (STP), which is $22.4\,L$.

Standard Temperature and Pressure (STP)

A reference condition for gas measurements defined as $0^{\circ}C$ ($273.15\,K$) and $1\,atm$ ($760\,torr$).

Ideal Gas Law

The mathematical relationship between pressure, volume, temperature, and number of moles of a gas expressed as $PV = nRT$.

Universal Gas Constant (R)

The proportionality constant in the ideal gas law, valued at $0.0821\,atm\cdot L\,mol^{-1}\cdot K^{-1}$ for pressure-volume calculations or $8.314\,J\,mol^{-1}\cdot K^{-1}$ for energy-related calculations.

Gas Density ($d$)

A property calculated as the mass per unit volume ($d = \frac{m}{V}$), which is directly proportional to the molar mass and pressure of the gas.

Dumas Method

An experimental procedure used to determine the molar mass of a volatile liquid by measuring the mass, volume, temperature, and pressure of its vapor state.

Dalton’s Law of Partial Pressures

The law stating that the total pressure of a mixture of nonreacting gases is the sum of the partial pressures of the individual gases ($P_{total} = P_1 + P_2 + P_3 + ...$).

Mole Fraction ($\chi$)

A dimensionless quantity representing the ratio of the number of moles of one component to the total number of moles in a mixture ($\chi_1 = \frac{n_1}{n_{total}}$).

Vapor Pressure

The pressure exerted by a vapor in equilibrium with its liquid phase at a given temperature, relevant when collecting a water-insoluble gas over water.

Kinetic-Molecular Theory (KMT)

A model describing gas behavior based on the postulates that particles have mass but negligible volume, are in constant random motion, and undergo elastic collisions.

Elastic Collisions

Collisions in which the total kinetic energy of the particles is conserved, meaning no energy is lost as heat or other forms.

Root-Mean-Square Speed ($u_{rms}$)

A measure of the average speed of gas particles at a specific temperature, defined by the formula $u_{rms} = \sqrt{\frac{3RT}{M}}$.

Effusion

The process by which a gas escapes from its container through a tiny hole into an evacuated space.

Graham’s Law of Effusion

The law stating that the rate of effusion of a gas is inversely related to the square root of its molar mass.

Diffusion

The movement of one gas through another due to the random motion of particles.

Mean Free Path

The average distance a gas molecule travels between successive collisions.

Collision Frequency

The number of collisions per unit time, obtained by dividing the most probable speed by the mean free path.

Real Gas

A gas that deviates from ideal behavior because its molecules have finite volumes and exert intermolecular forces on each other.

Van der Waals Equation

An equation for real gases that adjusts the ideal gas law for molecular volume (constant $b$) and intermolecular attractions (constant $a$).