Chemistry Notes: Concentration Units and Colligative Properties (Section 13.3–13.4)

Vocabulary-style flashcards covering concentration units (percent by mass, molality, mole fraction) and coll igative properties (vapor pressure lowering, Raoult's Law, osmotic pressure, and related concepts).

Henry's law constant (kH)

A proportionality constant in Henry's law relating the solubility of a gas to its partial pressure: C = kH × P. (Example: kH for O2 in water at 25°C can be found from C and P.)

Percent by mass

Mass of solute divided by the total mass of the solution, multiplied by 100%.

Molality (m)

Moles of solute per kilogram of solvent (units: mol/kg).

Mole fraction (X_i)

Ratio of the moles of a component to the total moles in the solution; XA = nA/(nA + nB + …).

Non-electrolyte

A solute that dissolves in water but does not dissociate into ions (no ions produced).

Strong electrolyte

A substance that fully dissociates in water into ions, producing many charge carriers.

Weak electrolyte

A substance that incompletely dissociates in water, producing fewer ions.

Colligative property

A physical property that depends on the number (concentration) of dissolved solute particles, not their identity.

Vapor pressure lowering

Dissolving a non-volatile solute in a volatile solvent lowers the solvent's vapor pressure.

Raoult's Law

In an ideal solution, Psolution = Xsolvent × P°solvent; Psolution is the observed vapor pressure, P°solvent is the vapor pressure of the pure solvent, and Xsolvent is the solvent's mole fraction.

P° solvent

Vapor pressure of the pure solvent.

P_solution

Observed vapor pressure of the solution.

X_solvent

Mole fraction of the solvent in the solution.

Osmotic pressure

The pressure required to prevent osmosis; a colligative property that depends on solute particle concentration.