Chem Semester Test

Mole

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* SI base unit used to measure the amount of a substance. 

Avogadro’s Number

6\.02x10^23

molar mass

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*  **mass in grams of one mole of any pure substance.** 

percent composition

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* percent by mass of each element in the compound.

empirical formula

smallest whole-number mole ratio of the elements.

molecular formula

specifies the actual number of atoms of each element in one molecule or formula unit of the substance.

hydrate

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* a compound that has a specific number of water molecules bound to its atoms.

stoichiometry

the study of quantitative relationships between the amounts of reactants used and the amounts of products formed by a chemical reaction.

mole ratio

a ratio between the numbers of moles of any two of the substances in a balanced chemical equation.

limiting reactant

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* limits the extent of the reaction and thereby determines the amount of product formed.

excess reactants

Reactants left over when a reaction stops

theoretical yield

represents the maximum amount of product that can be produced from a given amount of reactant.

actual yield

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* the amount of product produced when the chemical reaction is carried out in an experiment.

percent yield

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* **the ratio of the actual yield to the theoretical yield expressed as a percent.**

kinetic-molecular theory

describes the behavior of matter in terms of particles in motion.

elastic collision

one in which no kinetic energy is lost.

temperature

is a measure of the average kinetic energy of the particles in a sample of matter.

diffusion

is the movement of one material through another.

Graham’s Law of Effusion

states that the rate of effusion for a gas is inversely proportional to the square root of its molar mass.

pressure

defined as force per unit area.

Barometer

instruments used to measure atmospheric air pressure.

pascal

is equal to a force of one Newton per square meter or N/m2.

atmosphere

is equal to 760 mm Hg or 101.3 kilopascals.

dalton’s law of partial pressures

states that the total pressure of a mixture of gases is equal to the sum of the pressures of all the gases of the mixture.

dispersion forces

weak forces that result from temporary shifts in the density of electrons in electron clouds.

dipole-dipole forces

are attractions between oppositely charged regions of polar molecules.

hydrogen bond

are special dipole-dipole attractions that occur between molecules containing a hydrogen atom bonded to a small, highly electronegative atom with at least one lone electron pair.

viscosity

measure of the resistance of a liquid to flow and is determined by the type of intermolecular forces, size and shape of particles, and temperature.

surface tension

the energy required to increase the surface area of a liquid by a given amount.

surfactant

compounds that lower the surface tension of water.

crystalline solid

a solid with atoms, ions, or molecules arranged in an orderly, geometric structure.

unit cell

the smallest arrangement of atoms in a crystal lattice that has the same symmetry as the whole crystal.

allotrope

an element that exists in different forms at the same state—solid, liquid, or gas.

amorphous solid

one in which the particles are not arranged in a regular, repeating pattern.

melting point

the temperature at which the forces holding the crystal lattice together are broken, and the crystalline solid becomes a liquid.

vaporization

the process by which a liquid changes to a gas or vapor.

evaporation

vaporization that occurs only at the surface of a liquid.

vapor pressure

**the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature** 

boiling point

The temperature at which the vapor pressure of a liquid equals the external or atmospheric pressure

freezing point

the temperature at which

condensation

The process by which a gas or a vapor becomes a liquid

deposition

the process by which a substance changes from a gas or vapor to a solid without first becoming a liquid.

phase diagram

a graph of pressure versus temperature that shows in which phase a substance exists under different conditions of temperature and pressure.

triple point

the point on a phase diagram that represents the temperature and pressure at which all three phases of a substance can coexist.

boyles law

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* **states that the volume of a fixed amount of gas held at a constant temperature varies inversely with the pressure.**

absolute zero

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* **zero on the Kelvin scale.**  

charle’s law

 states that the volume of a given amount of gas is directly proportional to its Kelvin temperature at constant pressure.

gay lussac’s law

* **states that the pressure of a fixed amount of gas varies directly with the Kelvin temperature when the volume remains constant.** 

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combined gas law

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* states the relationship among pressure, temperature, and volume of a fixed amount of gas.

avogadro’s principal

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states that equal volumes of gases at the same temperature and pressure contain equal numbers of particles. 

molar volume

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* the volume 1 mol occupies at 0.00°C and 1.00 atm of pressure.

standard temperature and pressure (STP)

.00°C and 1.00 atm

ideal gas law

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* represented by R and is 0.0821 L•atm/mol•K when pressure is in atmospheres.

ideal gas constant

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* describes the physical behavior of an ideal gas in terms of the pressure, volume, temperature, and number of moles of gas present.

suspension

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* **mixtures containing particles that settle out if left undisturbed. Suspensions can also be separated by filtering.** 

colloids

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*  **heterogeneous mixtures of intermediate-sized particles (1 nm-1000 nm) that do not settle out, nor can they be filtered apart.** 

brownian motion

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* **the jerky, random movements of particles in a liquid colloid, from the results of particle collisions.**

tyndall effect

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* the scattering of light by dispersed colloid particles. 

soluble

A substance that dissolves in a solvent

miscible

Two liquids that are soluble in each other in any proportion

insoluble

A substance that does not dissolve in a solvent

inmiscible

Two liquids that can be mixed but separate shortly after

concentration

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* a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution.

molarity

* **the number of moles of solute dissolved per liter of solution.**

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molality

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* **the ratio of moles of solute dissolved in 1 kg of solvent.**

mole fraction

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* **the process of surrounding solute particles with solvent particles to form a solution.**

solvation

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* **the process of surrounding solute particles with solvent particles to form a solution.**

heat of solution

The overall energy change that occurs during solution formation

unsaturated solution

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* **solutions that contain less dissolved solute for a given temperature and pressure than a saturated solution.**

saturated solution

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*  **contain the maximum amount of dissolved solute for a given amount of solute at a specific temperature and pressure.**

supersaturated solution

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* contains more dissolved solute than a saturated solution at the same temperature.

henrys law

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* **states that at a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P).**

colligative property

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* **are physical properties of solutions that are affected by the number of particles but not by the identity of dissolved solute particles.**

vapor pressure lowering

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* **depends on the number of solute particles in solution. It is a colligative property of solutions.**

boiling point elevation

The temperature difference between a solution’s boiling point and a pure solvent's boiling point

freezing point depression

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* , is the difference in temperature between its freezing point and the freezing point of the pure solvent.

osmosis

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 the diffusion of a solvent through a semipermeable membrane.

osmotic pressure

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* **the amount of additional pressure caused by water molecules that move into the concentrated solution.**

energy

the ability to do work or produce heat.

law of conservation of energy

states that in any chemical reaction or physical process, energy is neither created nor destroyed.

chemical potential energy

energy stored in a substance because of its composition.

heat

energy that is in the process of flowing from a warmer object to a cooler object.

calorie

defined as the amount of energy required to raise the temperature of one gram of pure water by one degree Celsius (1°C).

joul

the SI unit of heat and energy.

specific heat

the amount of heat required to raise the temperature of one gram of that substance by one degree Celsius.

acidic solution

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*  contains more hydrogen ions than hydroxide ions.

basic solution

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* contains more hydroxide ions than hydrogen ions.

Arrhenius model

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* An acid is a substance that contains hydrogen and ionizes to produce hydrogen ions in aqueous solution.
* A base is a substance that contains a hydroxide group and dissociates to produce a hydroxide ion in solution.

Bronsted-lowery model

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* states that an acid is a hydrogen ion donor, and a base is a hydrogen ion acceptor.

conjugate acid

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*  the species produced when a base accepts a hydrogen ion.

conjugate base

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* the species produced when an acid donates a hydrogen ion.

conjugate acid-base pair

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*  consists of two substances related to each other by donating and accepting a single hydrogen ion.

amphoteric

can react with acids and bases

lewis model

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* a Lewis acid is an electron-pair acceptor, and a Lewis base is an electron-pair donor.

strong acid

Acids that ionize completely

weak acid

Acids that ionize only partially in dilute aqueous solutions

acid-ionization constant

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*  is the value of the equilibrium constant expression for the ionization of a weak acid.

strong base

A base that dissociates completely into metal ions and hydroxide ions

weak base

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*  ionizes only partially in dilute aqueous solution.

base ionization constant

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*  is the value of the equilibrium constant expression for the ionization of a base.