Mixtures, Solutions, Acids, Bases, and Salts. (last unit)

Solvent

The dissolving medium in a solution.

Solute

The dissolved particles in a solution.

Tyndall effect

The scattering of visible light by colloidal particles.

Colloid

A heterogeneous mixture containing particles that range in size from 1 nm to 1000 nm spread throughout a dispersion medium.

Surfactant

Any substance that interferes with the hydrogen bonding between water molecules and thereby reduces surface tension.

Surface tension

The inward force, or pull, that tends to minimize the surface area of a liquid.

Hydrate

A compound that contains water of hydration.

Nonelectrolyte

A compound that does not conduct an electric current in either aqueous solution or the molten state.

Emulsion

A colloidal dispersion of a liquid in a liquid.

Suspension

A mixture from which particles settle out upon standing because they are much larger and do not stay suspended indefinitely.

Strong electrolyte

A solute that completely, or almost completely, ionizes or dissociates in a solution, conducting electricity well.

Weak electrolyte

A solute that conducts electricity poorly because only a fraction of the solute in the solution exists as ions.

Electrolytes

All ionic compounds are ________ because they dissociate into ions and thus can conduct electricity.

Aqueous solution

Water that contains dissolved substances; it is a homogeneous mixture.

Dissolving process (Solvation)

The process of individual solute ions breaking away from the crystal. Solvent molecules surround the negatively and positively charged ions in a process called solvation, and the ionic crystal dissolves.

Colloid particle size

Particles are smaller than those in suspensions and larger than those in solutions.

Structure of ice

A regular open framework of water molecules held together by hydrogen bonds and arranged like a honeycomb.

Formula of a hydrate

Consists of the formula of the ionic salt followed by a dot and the number of water molecules associated with one formula unit.

Water's unique properties

High surface tension and low vapor pressure, which are both the results of hydrogen bonding.

Liquid water vs. Ice density

Molecules in liquid water are packed closer together than they are in ice.

Saturated solution

Contains the maximum amount of solute for a given quantity of solvent at a constant temperature and pressure.

Solubility

The amount of solute that dissolves in a given quantity of a solvent at a specified temperature and pressure to produce a saturated solution (usually expressed in grams of solute per 100 g of solvent).

Unsaturated solution

A solution that contains less solute than a saturated solution at a given temperature and pressure.

Miscible

Liquids capable of mixing in any ratios without separation.

Immiscible

Liquids that are insoluble in one another.

Supersaturated solution

A solution containing more solute than it can theoretically hold at a given temperature.

Henry's law

At a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P) of the gas above the liquid.

Concentration

A measure of the amount of solute that is dissolved in a given quantity of solvent.

Dilute solution

A solution that contains a small amount of solute.

Concentrated solution

A solution that contains a large amount of solute.

Molarity (M)

The number of moles of solute dissolved in one liter of solution.

Molality (m) & Mole fraction

Two additional ways of expressing the concentration of a solution, especially useful because they are proportional to freezing-point depression and boiling-point elevation.

Colligative property magnitude

Directly proportional to the number of solute molecules or ions present.

Diluting a solution

Does not change the total number of moles of solute in solution.

Three colligative properties

Vapor-pressure lowering, freezing-point depression, and boiling-point elevation.

Factors affecting dissolving speed

Stirring, temperature, and surface area.

Neutralization products

An acid and a base react to produce a salt and water.

Acidic solution

A solution in which [H+] is greater than [OH-]; pH is less than 7.0.

Basic (Alkaline) solution

A solution in which [H+] is less than [OH-]; pH is greater than 7.0.

Strong acids

Acids that are completely ionized in aqueous solution.

Weak acids

Acids that are slightly ionized in aqueous solution.

Sum of pH and pOH

Always equals 14 for any aqueous solution.

Monoprotic acids

Acids that contain one ionizable hydrogen, such as nitric acid (HNO3).

Diprotic acids

Acids that contain two ionizable hydrogens, such as sulfuric acid (H2SO4).

Triprotic acids

Acids that contain three ionizable hydrogens, such as phosphoric acid (H3PO4).

Conjugate acid

The particle formed when a base gains a hydrogen ion.

Conjugate base

The particle that remains when an acid has donated a hydrogen ion.

Conjugate acid-base pair

Two substances related by the loss or gain of a single hydrogen ion.

Salt hydrolysis pH effects

Salts producing acidic solutions contain positive ions that release protons to water; salts producing basic solutions have negative ions that attract protons from water.

Acid vs. Base taste & feel

Acids taste sour; bases taste bitter and feel slippery.

Arrhenius theory

Acids yield hydrogen ions (H+) and bases yield hydroxide ions (OH-) in aqueous solution.

Endpoint

The point of neutralization in a titration where the indicator changes color.

Self-ionization of water

The reaction in which water molecules produce ions: 2H2O ⇌ H3O+ + OH-.

Neutral solution

Any aqueous solution in which the concentrations of H+ and OH- are equal (pH = 7.0).

Ion-product constant for water (Kw)

The product of the concentrations of the hydrogen ions and hydroxide ions in water; Kw = [H3O+][OH-] = 1.0 x 10^-14.

pH formula

The negative logarithm of the hydrogen-ion concentration: pH = -log[H+].

pOH formula

The negative logarithm of the hydroxide-ion concentration: pOH = -log[OH-].

pH Scale range values

0 is strongly acidic, 7 is neutral, and 14 is strongly basic.

Lewis acid

An electron pair acceptor.

Lewis base

An electron pair donor.

Hydrogen ion

H+

Hydronium ion

H3O+

Hydroxide ion

OH- (or HO-)

Amphoteric

A substance that can act as both an acid and a base (like water).

Brønsted-Lowry acid

A hydrogen ion (proton) donor.

Brønsted-Lowry base

A hydrogen ion (proton) acceptor.

Buffer

A solution of a weak acid or weak acid base and one of its salts that resists drastic changes in pH.

Acid-base indicator

A substance whose acid and base forms have different colors in solution.

Henry's law equation

S1 / P1 = S2 / P2

Molarity equation

M = moles of solute / liters of solution

Molality equation

m = moles of solute / mass of solvent (in kg)

Dilution equation

M1 x V1 = M2 x V2

Percent by volume (% v/v)

(volume of solute / volume of solution) x 100%

Percent by mass (% m/m)

(mass of solute / mass of solution) x 100%

Mole fraction of solute A (XA)

nA / (nA + nB)

Mole fraction of solvent B (XB)

nB / (nA + nB)

pH + pOH

14

[H+] x [OH-]

1.0 x 10^-14

calculating molarity

To calculate the molarity of a solution, divide the moles of solute by the volume of the solution in liters.

The amount of solute that dissolves depends on?

The amount of solute that dissolves in a given solvent depends upon the temperature and pressure.

Solubility is expressed as?

Solubility is expressed in grams of solute per 100 g of solvent.

Molarity

moles of solute & liters of solution

Molality

moles of solute & mass of solution