AP CHEMISTRY STUDY GUIDE

AP CHEMISTRY STUDY GUIDE

• London dispersion forces: IMFs that occur between all molecules; oc- cur because of the random motions of electrons on atoms within molecules to create instantaneous polarities; molecules with more e- will have greater forces • substances with only London dispersion forces usually...: ... are gases at room temp, and boil/melt at extremely low temps • melting & boiling points of a covalent substance is almost always

than that of ionic substances: lower

• vapor pressure: the pressure exerted by a vapor over a liquid

• resonance structures: structures that occur when it is possible to draw two or more valid lewis electron dot diagrams that have the same number of electron pairs for a molecule or ion • formal charge: used to find which structure is most likely to occur; valence - assigned

• linear geometry: sp hybridization 0 lone pairs

ex. BeCl2 & CO2

• trigonal planar geometry: sp2 hybridization bond angles 120

• lone pairs: trigonal planar (three bonds) 1 lone pair: bent (two bonds)

• tetrahedral geometry: 4 e- pairs, sp3 hybridization angles 109.5

• lone pairs: tetrahedral (four bonds) [CH4, NH4+, ClO4-, SO4 2-, PO4 3-] 1 lone pair:

trigonal pyramidal (3 bonds) [NH3, PCl3, SO3 2-]

2 lone pairs: bent (2 bonds) [H2O, OF2, NH2-]

• trigonal bipyramidal geometry: 5 e- pairs, sp4 hybridization 0 lone pairs: trigonal bipyramidal (5 bonds) [PCl5, PF5]

1 lone pair: seesaw (4 bonds) [SF4, IF4+]

• lone pairs: t-shaped (3 bonds) [ClF3, ICl3] 3 lone pairs: linear (2 bonds) [XeF2, I3-]

• octahedral geometry: 6 e- pairs, sp5 hybridization 0 lone pairs: octahedral (6 bonds) [SF6]

• lone pair: square pyramidal (5 bonds) [BrF5, IF5] 2 lone pairs: square planar (4 bonds)

[XeF4] • maxwell-boltzmann diagrams: shows the range of velocities for molecules of a gas • effusion: the rate at which a gas will escape from a container through micro- scopic holes in the surface of the container • mole fraction: moles of substance/total moles in solution 1 / 2

• dissociation: when ionic substances break up into ions into solution

• electrolytes: free ions in solution that conduct electricity

• paper chromatography: the separation of a mixture by passing it through a medium in which the components of the solution move at different rates • retention factor: stronger the attraction between the solute and the solvent front is, the larger the Rf value will be • column chromatography: a column is packed with stationary substance, then the solution to be separated (analyte) is injected into the column where it adheres to the stationary phase, then the eluent solution is injected into the column. as the eluent solution passes through the stationary phase the analyte molecules will be attracted to it with varying degrees of strength based on polarity • distillation: the process that separates the substances in a solution based on their boiling points • precipitation reaction: a reaction in which an insoluble substance (salt) forms and separates from the solution • net ionic equation: an equation for a reaction in solution showing only those particles that are directly involved in the chemical change • limiting reactant: the substance that controls the quantity of product that can form in a chemical reaction; moles of each reactant divided by moles used in reaction

• gravimetric analysis: a type of quantitative analysis in which the amount of a species in a material is determined by converting the species to a precipitate that can be isolated completely and weighed

• when bonds are formed: ...energy is released

• when bonds are broken: ...energy is absorbed

• exothermic: products have stronger bonds than the reactants; heat is released,

- ”H

• endothermic: reactants have stronger bonds than the products; heat is ab- sorbed, + ”H • activation energy: the minimum amount of energy required to start a chemical reaction • catalyst: substance that speeds up a reaction by reducing the activation energy required by the reaction; provides an alternate reaction pathway; no effect on equilibrium conditions • oxidation number: H: +1

• entropy: ”S; a measure of the randomness or disorder of the system

• enthalpy: ”H; heat of a system at constant pressure

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