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Transcript of AP Chemistry Review

Stoichiometry Dimensional Analysis Sig Figs Must Always Follow When Doing Nonzero digist and zeros between nonzero digits are significant Zeros to the left of the first nonzero digit in a number are not significant Zeros at the end of a number to the right of the decimal point are significant Three Rules Addition & Subtraction: Round your answer to the same number of decimals as the measurement with the least number of decimals Multiplication & Division: Round your answer to the same number of sig figs as the measurement with the least number of sig figs Calculations using sig figs Prefixes:1 Kilo=1,000 bases1 Deka=10 bases1 Hecta=100 bases1 Base=1 base10 Deci=1 base100 Centi=1 base1000 milli=1 base10^6 micro=1 base10^9 nano=1 base Uses Carried Through Mole Most important unit Mole Conversions Used in Influences Answer to Conversions are: 1 mole=6.02 x 10^23 molecules1 mole=coefficient(6.02 x 10^23 atoms)1 mole=molecular mass Molar Mass grams/moles Units are Number of Moles is Numerator in Chemistry Gases Ideal gases behave according to KineticMolecularTheory Ideal GasLaw Used to find one of 4 variables for gas PV=nRT [(P1V1)/T1]=[(P2V2)/T2] Shows how changes to a variable affects other variables Used to find any of four variables relating to gas n represents number of moles Also known as Boyle's Law Charles' Law Gay-Lussac's Law Combined Gas Law P1V1=P2V2 Pressure and Volume are inversely related Volume and Temperature are directly related V1/T1=V2/T2 Temperature and Pressure are directly related P1/T1=P2/T2 All gases @ the same temperature have the same kinetic energy Part of First assumption Graham's Law If kinetic energy is only dependent on temperature Lighter Gases move Faster than heavier gases Most gases do not behave ideally Real Gases Volume of a gas is insignificant No attractions between gas molecules in an ideal gas Second Assumption Third Volume becomes significant Molecules attract each other Assumption Van Der Waals Equation Adjusted to fit nonideal conditions Works with real gases Thermo Enthalpy Entropy Free Energy Measure of molecular randomness or disorder Measure of spontaneity of a process Delta H H ( ) Represented as Delta S S ( ) Represented as Delta G G ( ) Represented as Bonds formed=released energyBonds broken=absorbed energy General rule is H=H(products)-H(reactants) Amount of energy capable to do mechanical work One way to find delta H is Applies to the equation H=E+PV H or Another way of finding H H=enthalpyE=Internal EnergyP=Pressure of systemV=Volume of system Where S or Things naturally go to a disordered state Increases Because G= H-(T S ) These three are all related by (-) (+) low (-)=always spontaneous(-) (+) high (-)=always spontaneous(+) (-) low (+)=never spontaneous(+) (-) high (+)=never spontaneous(+) (+) low (+)=not spontaneous at low temperature(+) (+) high (-)=Spontaneous at high temperature(-) (-) low (-)=Spontaneous at low temperature(-) (-) high (+)=not spontaneous at high temperature H S T G Various effects on spontaneity The more energy molecules have, the more random their motion Solid --> LiquidLiquid --> Gas Physical change Entropy and Entropy and Chemical Change More moles of gas on product side=(+)S(system) and entropy increases More moles of gas on reactant side=(-)S(system) and entropy decreases Spontaneity Exothermic Something that happens without outside interventions Reactions can be AtomicStructures Subatomic Particles History of Atom Electron Configurations PeriodicTable PeriodicTrends Families Organization Valence Electrons Atomic Radius Ionization Energy Electron Affinity Electronegativity Reactivity Alkali Metals Alkaline Earth Metals Transition Metals Halogens Noble Gases Lanthanide Nuclear Decay Nuclear Stability Half-Life Used to convert between units Limiting Reagents Limits amount of product formed 1) Write balanced equation 2) Calculate product formed from each reactant individually 3) Circle answer that is the smallest Three rules All atoms contain Proton Neutron Electrons AtomicNumber Atomic Mass P + N Nucleus Located inside Located inside Located outside Famous Scientists/Experiments Atom went through many changes thanks to John Dalton & his atomic theory First scientist to have evidence on atom 1)Matter is made of tiny indivisible particles called atoms 2)Atoms of the same element are identical 3)Atoms of different elements are different 4)Elements combine to form new compounds 5)Atoms are merely rearranged in a chemical reaction Isotopes P + N Same number for atoms of the same element Different amount for atoms of the same element Same number as protons Five parts Discovery of isotopes disproved this part of Dalton's theory Thomson Found that atoms have a negatively charged part Discovery of Rutherford & gold foil experiment Discovered that atoms are mostly empty spaces with a small positively charged dense spot Discovered Chadwick Discovered Determined that a neutral particle was located in nucleus Bohr's Model Average weighed mass of all the isotopes for a given element Hoped to clarify location of electrons Orbitals Orbitals correspond to different energy levels Quantum Model Limitation Bohr model doesn't work with more than one electron Takes care of this fault Heisenberg Uncertainty Principle Location & speed of electrons can't be found simultaneously Electrons are still found in orbitals The order in which orbitals fill with electrons Aufbau Principle Hund's Rule Pauli Exclusion Principle Three rules Electrons occupy 1 per orbital until doubling up Orbitals fill lowest energy to highest energy Each electron has a unique address States That Elements fall into one of three categories Metals Non-Metals Metalloids Rows Columns Also known as Protons of an element gives you the Atomic number increases as you go across a row Located on columns 13-18 Found on staircase along columns 13-17 Located on columns 1-12 There are eighteen There are seven Form anionsDull appearanceBrittleNot ConductiveDoes not react w/ AcidsMost are gases @ room temp. Characteristics Have characteristics of both metals and non-metalsB, Si, Ge, As, Sb, Te, At Characteristics Forms cationsShinyConductiveMalleablereacts w/ gasesSilver/gray colorDuctileSolid @ room temp Characteristics Energy Levels Column 1 Column 2 Column 18 Columns 3-12 Column 17 Actinide Between Columns 3-4, Row 6 Between Columns 3-4, Row 7 Columns 1-2 is s-orbital, 13-18 is p-orbital Columns 3-12 is d-orbital, lanthanides and actinides are f-orbital +1 +2 +3 -3 -2 -1 OxidationNumbers Columns 1, 2, 13, 15, 16, & 17 Have their own Column 1 has Column Column Column Column Column 2 has 13 has 15 has 16 has 17 has Endothermic Either or Equilibrium Le Chatelier Equilibrium system can be changed Change in Volume Change inTemperature Change inConcentration Increasing temperature shifts the system to the products and makes K value bigger Decreasing temperature shifts the system to the reactants and makes K value smaller Increasing temperature shifts the system to the reactants and makes k value smaller Decreasing temperature shifts the system to the products and makes K value bigger Changes K First stress Second Stress Third stress Only stress that speed of electrons Inert gases= no shift Effect of inert gases Finding the average mass of one mole for an element Determined by Affects Shifts the equilibrium system to the opposite side of the added substance Addition of a substance that is part of the system Shifts the equilibrium system to the same side of the removed substance Removal of a substance that is part of the system Decreasing Volume Increasing volume Decreases the pressure and shifts the system to the side of the reaction that has more moles of gas Increases the pressure and shifts the system to the side of the reaction that has less moles of gas The equilibrium position will shift in a direction that will decrease the change associated w/ a stress states that Most stresses do not change k value Forward and Reverse Reactions Chemical reactions are reversible at same rate happens Double arrow Shown using Molecules of products collide w/ enough energy to re-form the reactants Reverse reaction is when Moles of solute dissolved in 1L of solvent Molar Solubility greater than .1M solubillity Soluble Less than .1M solubility Insoluble You just Find X ICE Table One method of solving Equilibrium problems Kc Kp Partial Pressures If using If using Concentrations Then use then use Kp=Kc(RT)^ n Used in to convert to Kc Used in to convert to Kp Equilibrium Concentrations Helps you solve for Initial concentration First given Must find Change in concentrations K Expression Products on top reactants on bottom Can find concentrations Solids or pure liquids Does not include If you know K Ksp Uses Equilibrium solubility product Is the Solid dissolving written as The value of C Equilibrium Constant All equilibrium equations have this Any form of K It is Ratio of products to reactants at equilibrium Tells you Extent of a reaction Lets you predict the tendency for reaction to occur & if it is @ equilibrium K is much greater than 1 K is much smaller than 1 If If Then products are favored and reaction goes to near completion Then reactants are favored and reaction does not occur to any significant extent Utility of Q Ratio of initial concentrations of products to reactants Both used to determine which way system will shift System at equilibrium Products are too big and system shifts towards reactants Reactants are too big and system shifts towards products If Q=K If Q>K If Q<K 4% Rule Used when equilibrium constant is small Ignore the X change for substances that had an initial concentration (Smaller than or equal to 10^-5) The change must be less than or equal to 4% of the initial value States that ([(Coefficient)(X)]/Initial value)x100% General formula is kinetics RateLaw Uses a mathematical concept known as Two types of rate laws Integrated rate law Differential rate law Experimental data Rate 1 Rate 2 -------- = [Reactant 1] [Reactant 2] ^n ----------------- ( ) Rate as a function of concentration An expression that shows how the reaction rate depends upon the concentrations of reactants Order of Reaction-zero, first, second concentration as a function of time Overall Order Add the exponents of the rate law Different types of integrated rate laws zero first second [x]=-Kt+[x] o ln[x]=-Kt+ln[x] o (1/[x])=Kt+(1/[x] ) o Graphs of zero, first, second order ln[x] vs. t (1/[x]) vs. t [x] vs. t Half-Life Time needed for the concentration of a reactant to be cut in half =[x] /2K =.693/K =1/(K[x] ) o o t t t 1/2 1/2 1/2 ReactionMechanism A reaction happens in steps a reaction takes place Two requirements 1) The sum of elementary steps must give the overall balanced equation for reaction (Hess's Law) Mechanism must agree with the experimentally determined rate law Elementary Steps own rate law Slow, Fast, or Fast Equiibrium Intermediates Catalysts Unstable Formed first as a product then immediately used up as a reactant Rate Determining Step is the slow step differential rate Seen first as a reactant then used up as a product Potential Energy Diagram Shows you how to make the reaction proceed ActivationEnergy MolecularOrientaion Energy of collisions get consumed Energy required to produce the products Reaction faster reaction Collision Theory Acids and Bases Arrhenius Acids Substances that produce protons (H+) in solution Strong Acids Svante Arrhenius Fully Dissociatein H2O Extremely high Ka values Bronstead-Lowry Base Bronstead-Lowry Acid A proton donor Weak Acids Low Ka value Partially Dissociate in H20 HA-->H^+ + A^- HA<-->H^+ + A^- Conjugate Bases Johannes Bronstead Act as a base Lewis Acid An electron pair donor A proton acceptor Arrhenius Base Any substance that releases OH^- ions in solution Weak Bases Low Kb value What is left over from the acid after it loses the proton pH Strong Bases Lewis Base An electron pair acceptor G. N. Lewis pOH Conjugate Acids Partially dissociate in H2O B + H2O<--> HB^+ + OH^- B + H2O--> HB^+ + OH^- Fully Dissociate in H2O Extremely high Kb value Act as acids Product formed as a result of the base accepting a proton Tells how acidic a solution is Tells how basic a solution is Measures concentration of H^+ or H3O^+ Measures concentration of OH^- Calculating pH Calculating pOH pH=-log[H^+] pH=-log[H3O^+] or pOH=-log[OH^-] pH=14-pOH pOH=14-pH Ka Kb Equilibrium constant of acids Equilibrium constant of bases A measure of the strength of a weak acid A measure of the strength of a weak base Kw Kw=(Ka)(Kb) 1.0 x 10^-14 Equilibrium constant of water Solutions Homogenous Mixture Solute Solvent Individualcomponents Getsdissolved Doesdissolving Make roomfor solute Heat ofFormation Solute willdissolve Solute willnot dissolve FactorsAffectingSolubility Likedissolveslike Increasing pressureincreases solubility Gassolutes solid solutes Increasing temperatureincreases solubility Increasing temperaturedecreases solubility Concentrations Fourkinds Molarity Molality Mole Fraction Percent Mass Types of Solution Electrolytes Non-Electrolytes Don't conduct electricity Sugar Conduct Electricity Sodium Chloride Colligative Properties Solutes affects physical properties of the solvent Many types of colligative properties Vapor Pressure Raoult's Law Boiling Point Depression Freezing Point Elevation Osmotic Pressure Moles of Solute Liters of Solution Moles of Solute Kg of Solvent Moles of Solute Moles of Solution mass of solute mass of solution 100 Pressure of gas above the liquid of the same substance non-volatile solute The v.p. of a solution is lower than the v.p. of the pure solvent P(solution)=X(solute)P (solvent) o Boiling Point of a solution is higher than the Boiling point of pure solvent T=Kb m Freezing point of a solution is lower than the freezing point of pure solvent T=Kf m The driving force for the H20 movement =MRT Van't HoffFactor amount of solute disolved Number of pieces a substance will break into per mole of solute i More than an order of 3 Reaction rate increases with increasing concentration of reactants Reaction rate increases with increasing temperature Reactant that gets used up first is the Convert between different units helps 6.02 x 10^23 items contains (P+ )(V-nb)=nRT n 2 a V 2 ---- Formula is r1 M2 r2 M1 ---- --- = Formula is equation is Equation is equation is Changes in each of its variables affect the other variables lets you figure out how Energy Major theme in The capacity to do work or produce heat Is the Joules (J) measured in 1st Law of Thermodynamics The most important law is the Law of conservation of energy also known as Energy can not be created nor destroyed Energy can only be transferred from one form to another is related in that First part states that Second part states that Potential Kinetic Two forms of energy there are first one second one Stored in bonds between atoms Measured by temperature it is it is energy is released to the surroundings energy is absorbed from the surroundings cold hot feels feels identified when identified when Heat Transfer of energy between two objects due to temperature difference Changes is the force acting over a distance Work changes is the fast or slow can happen it is everything in the universe is in constant caused by increase in entropy enthalpy, temperature, and entropy relates no charge 1 amu The second one is has weighs Negativecharge 0 amu has weighs cathode ray tubes used 1932 his discovery was around Began in ancient greece Models used to study atom the third one is positive charge 1 amu has a weighs area of high probability of finding an electron four orbitals there are are Solids and Liquids CrystallineSolids Types of Crystalline solids Crystals Very organized arrangements an attractive force between adjacent molecules of the same substance Ionic Molecular Atomic Lattice points of crystals Amorphous Solids Types of atomic solids Network Metallic 8A lattice structures Variety of solids Significant disorder in their arrangement no long-range order of the positions of the solids ions StableHigh melting points electrostatic forces NaCl Molecules IMF low melting pointnot conductive CO2 Atoms London Dispersion MetalCations conductiveductilemalleable Metallic Bonds ABA, ABCA Non-metal atoms Covalent Bonds BrittleNon-Conductiveextremely high melting point SiO2, diamond Group 8A atoms London Dispersion Ar Lines Lattice Points Two major solids there are Either or lines lines lines lines lines lines lattice points lattice points lattice points lattice points lattice points lattice points Characteristics Characteristics Characteristics Characteristics Ex Ex Ex Ex 1st 2nd 3rd 1st 2nd 3rd 3 There are Three Determined by there is a wide Best Packing have are are not have have represented by contains contains held by same thing Properties of Liquids there are many Low compressibility have Fluid are high density Surface Tension has Capillary Action Viscosity has has rising of a liquid in a narrow tube adhesion and cohesion is the done by two things liquids resistance to flow IMF, molecule size, and complexity is Caused by Liquid doesn't want to spread out means the Uneven distribution of IMF happens because IntermolecularForces IMF stands for IMF stands for is an London Dispersion Dipole-Dipole H Bonding Weakest IMF All Covalent Substances Polar Covalent Molecules Attraction of opposite dipoles in adjacent molecules Larger force of attraction F, N, O Same thing 1 2 3 is the found in found in caused by can only be has gases can be solutes Heat of Formation=Enthalpy The 8A elements are the Noble Gases The half life for all nuclear reactions is first order The Phase diagrams for both topics look for the energy required to make the reaction proceed are all different types of equilibrium constants Ka, Kb, and Kw Vapor Pressure has the same definition in both solutions and solids and liquids Key: Connection to topicConnects Major concept to major conceptConnects major concept to detailConnects detail to detailEquationDetailMajor ConceptTopicConnection between topics Alpha Beta Gamma Positron Emission Electron Capture A particle equivalent to a helium nucleus is released from the nucleus Subtract four from the mass number and subtract two from the atomic number The nucleus changes a neutron into a proton and an electron and releases the electron The mass number remains the same but you add one to the atomic number electromagnetic radiation that have no mass and charge Accompany other forms of nuclear decay The nucleus captures a low energy electron and combines it with a proton to form a neutron The mass number remains the same but you subtract one from the atomic number The nucleus changes a proton into a neutron and a positron, and releases the positron The mass number remains the same but you subtract one from the atomic number The nucleus will try to gain protons and lose neutrons The nucleus will try to lose protons and gain neutrons Seen mainly in very large nuclei (atomic numbers of 60+) The time it takes for half of the substance to decay some form of time (sec, min, hrs, days, years, etc.) Fission Fusion Splitting of a large unstable nucleus into two smaller nuclei Nuclear bombs and nuclear power plants Combining two small nuclei to make a large, more stable nucleus Sun and atomic bombs extremely high temperatures Mass Defect The difference in mass when protons and neutrons come together to form a nucleus Released as energy Binding Energy Energy required to decompose the nucleus back into protons and neutrons E=mc 2 Energy in joules mass in kg more stability Bonding Covalent Ionic Metallic Metal and non-metals The metal cation to the non-metal anion Non-metals Sharing of electrons between the non-metal atoms Lewis Structures A picture of a compound that shows how the atoms are bonded together and how the valence electrons are distributed 1) Count the valence electrons 2) Draw the skeletal structure 3) Distribute valence electrons so that each atom has eight of them 4) Determine the formal charge for each atom VSEPR (Shapes) Electrons found in bonds and lone pairs around the central atom repel The number of atoms attached to the central atom and the number of lone pairs around it Formal Charge F.C.=V.E.-(Bonding Pairs)-(Unbonded electrons) A stable molecule will have each atom with a F.C. of zero or as close to zero as possible Resonance Structures Two or more structures with the same skeletal structure but different arrangements Must draw both structures and separate them with a double headed arrow Octet Exceptions Hydrogen Beryllium Boron All elements in the third row and below Put the extra valence electrons on the central atom as lone pairs Hybridization They morph into hybrid orbitals One hybrid orbital Sigma Bonding Pi Bonding Bonds formed from hybridized orbitals overlapping are not sigma bonds Single bonds Bonds formed between unhybridized orbitals Double and triple bonds Attachments Hybridization 234567 spspspsp dsp dsp d 2

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3 Electrochem Galvanic Cells Uses redox reactions to generate electric current LEO goes GER Mnemonic device used in this is LEO=losing electron oxidationGER=Gaining electron reduction Where the acronyms Stand for Electrode Salt Bridge Wire Anode Cathode Parts that make up a galvanic cell Electrons Oxidation Reducing Agent gets oxidized Negatively charged holds the is Generates is the substance that handles electron donor is an loss of electrons increases is a Reduction Oxidizing Agent Electrons positively charged is handles holds the receives oxidizing state Decreases oxidizing state gain of electrons is a It is GER in It is LEO in getsreduced it gets Electron acceptor is an Capture moving electrons through a wire separates oxidation half reaction from reduction half reaction to (+) and (-) ions Charge holds Balances out connects Metal Platinum Made from a If no metal was present in oxidation or reduction, then use ElectronFlow ensures that this occurs handles the Movement ofelectrons is known as the anode to cathode goes from Cell Potential The amount of electricity generated by the cell Volts E O measured in represented by All cells contain this ElectrolyticCells Ion flow of salt bridge is reversed negative cell potential Opposites Forcing currents backward Charging a battery similar to Anode and Cathode reverse the roles of are not spontaneous positive cell potential is spontaneous Chemical reactions occur b/c reactants are colliding with each other Effect of more reactant molecules Effect of temperature Tells you Low Activation Energy Shows you the completion of the Minimum energy required to make reaction proceed must be enough Needed to make reaction happen Molecules must be the same angle to collide means that to overcome activation energy lower the do not How to identify in a reaction mechanism stablize catalysts how to identify in a reaction mechanism are usually intermediates can appear in contain their can be either the rate is the the rate law for this step must satisfy this criteria the second one is the first one is There are for this shows you how is a series of catalysts can appear in there are first type second type plotting plotting plotting gives you straight line for line for line for gives you straight gives you straight Equation is equation is equation is there is there are shows shows determined by plug in values uses tells you the multiple equations for half-life first second zero definition