# SAT II Chem

## 105 terms

### pressure

force per unit area

### diffusion

random motion of gases in moving from one position to another

### effusion

the passage of a gas through a tiny orifice into an evacuated chamber

### Graham's Law

the rate of effusion of a gas is inversely proportional to the square root for its molecular mass:
(rate A/rate B)=sqrt(molecular mass A/molecular mass B)

1 atm and 273 K

### Charles's Law

If the pressure remains constant, the volume of a gas varies directly as the absolute temperature:
initial (v/t) = final (v/t)

### Boyle's Law

if the temperature remains constant, the volume of a gas varies inversely as the pressure changes:
initial (pv) = final (pv)

### Combined Gas Law

initial (pv/t) = final (pv/t)

### Gay-Lussac's Law

at constant volume, the pressure of a given mass of gas varies directly with the absolute temperature:
initial (p/t) = final (p/t)

### Dalton's Law of Partial Pressures

when a gas is made up of a mixture of different gases, the total pressure of the mixture is equal to the sum of the partial pressures of the components; the partial pressure of the gas would be the pressure of the individual gas if it alone occupied the volume:
total P= P of gas 1 + P of gas 2 + P of gas 3...

PV=nRT

R

### 6.02 * 10^23

the number of molecules of Hydrogen in a 1-liter container is exactly the same as the number of molecules of carbon dioxide or any other gas in a 1-liter container

### molar mass

the mass of 1 mole of that compound expressed in grams

### 22.4 L

one mole of any gas at STP occupies:

### Gay Lussac's Law (of Combining Gases)

when only gases are involved in a reaction, the volumes of the reacting gases and the volumes of the gaseous products are in a small-whole-number ratio to each other

### percent yield

the ratio of the actual yield to the theoretical yield, multiplied by 100%

### mass

quantity of matter a substance possesses

### inertia

property of mass to reist a change of position or motion

### density

relationship of mass to a unit volume

### solid

has both definite size and shape

### liquid

has definite volume but takes shape of container

### gas

has neither definite shape nor a definite volume

### distinct substance

can be subdivided into the smallest particle that still has the properties of that substance

### compound

when two or more types of atoms join together in a definite grouping

### physical properties

can be observed with our senses

### chemical properties

can be observed in regard to whether or not a substance reacts with other substances

### physical change

alters some aspect of the physical properties of matter

### chemical change

change in the composition and structure of a substance; always accompanied by energy changes

### exothermic

when energy is given off

### endothermic

when energy is absorbed

### activation energy

the energy necessary to get the reaction going

### Law of Conservation of Matter

in a chemical change, matter can neither be created nor destroyed, but only changed from one form to another

### energy

the capacity to do work

### isotopes

atoms of the same element that have different masses

### electronegativity

the number that measures the relative strength with which the atoms of the element attract valence electrons in a chemical bond

### electron affinity

the energy change that occurs when an electron is gained by a neutral atom

### ionization energy

the amount of energy needed to remove an electron from its atom

### ionic bond

when the electronegativity differs by 1.7 or more

### polar covalent bond

when the electronegativity difference is between 0.4 and 1.6

### intermolecular forces (van der waals forces)

attractions between molecules

### dipole-dipole

the force of attraction between polar molecules

### London dispersion forces

caused by instantaneous dipoles; very weak attraction

### hydrogen bonds

special dip-dip bonding

### VSEPR

structural theory that deals with bond angles

### hybridization

theory that describes changes in the orbitals that contain the valence electrons

### sigma bond

bond between s orbitals or an s orbital and another orbital

### pi bond

bond between two p orbitals

### polyatomic ion

group of elements that act like a single atom in the formation of a compound

### Brownian movement

particles' zigzag path

### viscosity

the friction or resistance to motion that exists between the molecules of a liquid when they move past each other

### surface tension

imbalance in forces at the surface of a liquid

### capillary action

the attraction of the surface of a liquid to the surface of a solid

### meniscus

concave liquid surface

### phase equilibrium

when the rates of condensation and evaporation are equal

### Le Chatelier's Principle

When a system at equilibrium is disturbed by the application of a stress (a change in temperature, pressure, or concentration), it reacts so as to minimize the stress and attain a new equilibrium position

### equilibrium vapor pressure

the pressure of the molecules in the vapor that are in equilibrium with the liquid

### critical temperature

the temperature above which the liquid phase of a substance cannot exist

### critical pressure

the minimum pressure required to liquefy a gas at its critical temperature

### crystalline solids

have a 3D representation much like a brick wall (with a repeating structure)

### amorphous solids

have a random structure

### polycrystalline solids

an aggregate of a large number of small crystals (crystals are ordered but arranged in a random way...)

### sublimation

vaporize without passing through the liquid phase

### heat of fusion

amount of energy needed at the melting point to cause the change of phase

### triple point

the point at which the solid, liquid, and vapor phases may all exist at equilibrium

### synthesis

the formation of a compound by uniting its components

### anhydrides

oxides that react with water to form two classes of compounds--acids and bases

### solute

the substance dissolved

### solvent

the dissolving medium

### miscibility

ability for two liquids to completely dissolve in each other

### percentage concentration

the percent of solute in solution

### specific gravity

the ratio of the mass of a substance to the mass of an equal volume of water

### molarity

the number of moles of a substance dissolved in 1 liter of solution

### molality

the number of moles of the solute dissolved in 1000 g of solvent

### normality

the number of gram-equivalent masses of solute in 1 liter of solution

### decomposition

breakdown of a compound to release its components as individual elements or other compounds

### single replacement

when one substance displaces another (in a compound)

### double replacement

exchange of "partners" in a compound

### heat of formation

the number of calories absorbed when a mole of the compound in question is formed by the direct union of its elements

### heat of combustion

the heat evolved when 1 mole of substance is completely oxidized (in combustion reactions)

### entropy

the measure of the degree of disorder

### standard state

(for heat data) 25 degrees C and 1 atm

### standard enthalpy of formation

the change in enthalpy that accompanies the formation of 1 mole of a compound from its elements with all substances in their standard states at 25 degrees C

### Hess's Law of Heat Summation

when a reaction can be expressed as the algebraic sum of two or more other reactions, the heat of the reaction is the algebraic sum of the heats of these reactions

### First Law of Thermodynamics

the total energy of the universe is constant & cannot be created or destroyed

### catalyst

substance that is introduced into a reaction to speed up the reaction by changing the activation energy

### Law of Mass Action

the rate of a chemical reaction is proportional to the product of the concentrations of the reactants

### reaction mechanism

the series of steps by which the reacting particles rearrange themselves to form the products of a chemical reaction

### equilibrium

when the rate of the forward reaction equal the rate of the reverse reaction

k(eq)

### Second Law of Thermodynamics

the entropy of the universe increases for any spontaneous process

### free energy

combined factors of enthalpy and entropy

### phenolphthalein

pink in a basic solution

### litmus

red in acid, blue in base

### amphoteric

substances that can act as either acids or bases

### electrolyte

a substance that conducts an electric current

### half-cell

a single electrode immersed in a solution of its ions

### anode

electrode where oxidation takes place

### cathode

electrode where reduction takes place

### reduction

gain of electrons

### oxidation

loss of electrons

### electrode potential

the energy required to remove electrons from metallic atoms

### electroplating

when electrolysis is used to coat a material with a layer of metal

### alloy

mixture of two or more metals