Pharmaceutics & DDS - Exam 2 - Physiochemical Properties of Solids, Liquids, & Gases

what is sublimination?

what a substance converts directly from a solid to a gas

what is lyophilization?

freeze drying

due to the random and rapid collisions of gas molecules, gas often exerts ____________

pressure

according to the Ideal Gas law, what is the relationship between P, V, and T?

- T is directly proportional to both P and V (as T increases, P increases; as T increases, V increases)

- P and V are inversely related (as P increase, V decreases)

the Ideal Gas law is a combination of what 3 other laws?

- Boyle's law

- Charles' law

- Gay-Lussac's law

what is Boyle's law?

relates the V and P of a given mass of gas at a constant T

P ∝ 1/V, or PV = k

what is Charles' law?

relates the V and absolute T of a given mass of gas at a constant P

V ∝ T, or V = kT

what is Gay-Lussac's law?

relates the P and absolute T of a given mass of gas at constant V

P ∝ T, or P = kT

what are the assumptions made by the Ideal Gas law?

- no intermolecular forces exist

- collisions are perfectly elastic

- no energy exchange occurs

P1V1 / T1 = P2V2 / T2

REFRESHER - what is the Ideal Gas law equation?

PV = nRT

what is the relationship between the Ideal Gas law and molecular weight of a gas?

remember moles = g/mw

substitute g/mw in for "n" in PV = nRT

mw = (gRT)/PV

T/F: cooling a gas reduces its kinetic energy

TRUE

what happens when you pressurize a gas?

applying pressure to a gas leads to increased contact between the gas molecules

- this encourages van der Waals interactions, passing the gas into its liquid state (liquids are denser than gas!)

T/F: both gases and liquids can assume a definite volume

FALSE

- liquids can assume a definite volume, but gases cannot

what is vapor pressure of a liquid?

pressure at dynamic equilibrium between a liquid and its vapor, when molecules escape into the gas phase

how does temperature affect vapor pressure?

vapor pressure increases as temperature increases

solids can be classified as either...?

crystalline or amorphous

what are crystalline solids?

solids arranged in a fixed geometrical pattern known as lattice

- ex: diamonds, NaCl, ice

what is polymorphism?

when a crystalline solid occurs in >1 crystal form

- polymorphs have difference physical properties (melting point, solubility)

- ex: albuterol

what are amorphous solids?

solids that lack a definite arrangement

- molecules are arranged randomly (no lattices) and are not as stable as crystals

- aka super-cooled liquids

- ex: graphite

T/F: amorphous solids exhibit polymorphism

FALSE

- amorphous solids do NOT exhibit polymorphism