SAT II Chem
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105 terms
Terms | Definitions |
|---|---|
 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) |
| STP | 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... |
| Ideal Gas Law | PV=nRT |
| 0.0821 L atm/mol K | R |
| 6.02 * 10^23 | Avogadro's number |
| Avogadro's Law | 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 |
| equilibrium constant | 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 |
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