Review Material For Mid Term
Review Material For Mid Term Chem 142
Popular in General chemistry
Popular in Chemistry
This 13 page Study Guide was uploaded by Jessie Yuan on Monday October 26, 2015. The Study Guide belongs to Chem 142 at University of Washington taught by Dr. Li Xiaosong in Fall 2015. Since its upload, it has received 278 views. For similar materials see General chemistry in Chemistry at University of Washington.
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Date Created: 10/26/15
Review Material For CHEM142 Mid Term Jessie Yuan University of Washington These materials basically come from ALEKS and the LECTURES they conclude all the hard and triggering knowledge points hope I can help you all with this Thank you 0 ALL KINDS OF CHLORIC ACID Hydrochloric acid HCL Perchloric acid HCIO4 Chloric acid HCIO3 Chlorous acid HCI02 Hypochlorous acid HCIO 0 STANDARD CHEMICAL AND PHYSICAL STATES OF THE ELEMENTS IITIEtEIIIS M n onmetalls I I I I I I I 39 I I 39I 39 I i I i I I II I I I I I 39I I I I I II I I I 2 i iI Q Hg Mfg o ENERGY AND LIGHT POTENTIAL ENERGY The energy an object has by virtue like gravity PEmg h KINETIC ENERGY The energy an object has by virtue of its motion KE12mvquot2 CHEMICAL INTERNAL ENERGY EEPEK MOLECULAR KINETIC ENERGY 1 Transition 2 Rotation 3 Vibration MOLECULAR POTENTIAL ENERGY IntermolecularAttractions EXOTHERMIC Evolution of the system that results in heat transfer to the surroundings ENDOTHERMIC Evolution of the system that results in heat transfer to the system CHARACTERIZING LIGHT 1 Wave length x lambda the distance between the consecutive peaks in the wave 2 Frequency v nu the number of waves or cycles that pass a given point in space per second 3 EnergyE Increases with v decreases with A The photoelectric effect KE12mvquot2h v photon CD WORKFUNCTION CDh v0 0 IONIZATION ENERGY AND ATOMIC SIZE Atemic Size Increases 1I39Il39ith Arrews Ienizetien Enercl39lr Increases 1I39Il39ith Arrews O ELECTRON CONFIGURATION ttotal 2 EIEEIFEIFIE I a 3 quot ttotal 11 Electrons 153232 is l39 t r se 39 ttotal 12 Electrons 13233322jihggi Ikequot3 3x If x it talz 2n ElectWE HEESEEF USHE3335432 diffM If if if IIIIZIIIEII 33 E IEEIWI39IE 52232EffigyIj sj cjggg ducliji39 s eff uquot quotJimsf Pn39quot Ep t39ri gj xt u lnglf39iduniIiJHEI EiII wEE g fquot v t39 ferrquot ttotal SE EIEEIFEIFIE I itsa gj isa zijristy sir l39iuji iaa silrmaji attit15a fquot m ttotal 3392 Electrons wequot a O USING PLANK39S CONSTANT IN THE quotALTERNATIVE UNIVERSEquot SETTING An imaginary Plank39s constant is given to create an alternative universe In that universe which of the following objects would require quantum mechanics to describe that is would show both particle and wave properties Which objects would act like everyday objects and be adequately described by classical mechanics Two choices classical mechanics or quantum mechanics Comparing de Broglie wavelength of the quotalternate universequot to its size tells you whether each object must be described by quantum mechanics or not Any object with a de Broglie wavelength much smaller than its size can safely be described by classical mechanics and will act like an everyday object DB Wavelengthltsize of the object classical mechanics DB Wavelengthgtsize of the object quantum mechanics The key to knowing whether you need quantum mechanics to describe an object is its de Broglie wavelength A property of a moving object that can be used to determine whether the object shows waveparticle duality That is by using its de Broglie wavelength you can decide whether an object can be accurately described by classical mechanics or whether quantum mechanics must be used h A In this equation h stands for the Planck constan and p stands for the momentum of the object p h Often it39s useful to use the fact that the mome A ntum p of an object equals its mass m multiplie d by its speed v o SCHRODINGER EQUATION Schrodinger Equation is a wave equation in terms of the wave function which predicts analytically and precisely the probability of events or outcome Kinetic Potential Energy Energy Classical 1 1 H 2 2 armomc oscrllator Conservation ol 2 quotW 2 kx E example Energy Newton39s Laws F ma 39kquot Quamum 2 The energy becomes Conservation at i l kx 2 the Hamiltonian operator Energy 239 2 Wavefunction Schrodinger Equation M h 8 Energy eigenvalue 39quot makm tor the s tem transition to 39gt39 x 39gt X VS a 393 9 quot quot39 239 2 The form of the Hamiltonian physical variables h a take me tom 0 H p 1 2 operator tor a quantum quotoperatorsquot 2 3x2 2 harmonic oscillator The kinetic and potential energies are transformed into the Hamiltonian which acts upon the wave function to generate the evolution of the wave function in time and space The Schrodinger equation gives the quantized energies of the system and gives the form of the wave function so that other properties may be calculated 0 WAVE FUNCTION AND PHOTOELECTRIC EFFECT The Photoelectric Effect The photoelectric effect is the observation that many metals emit electrons when light shines upon them Electrons emitted in this manner can be called photoelectrons According to classical electromagnetic theory this effect can be attributed to the transfer of energy from the light to an electron in the metal From this perspective an alteration in either the amplitude or wavelength of light would induce changes in the rate of emission of electrons from the metal 1 The maximum kinetic energy mm of an ejected electron is given by rmax E53 where h is the Planck constant and is the frequency of the incident photon The term ff is the work function sometimes denoted f or 133 which gives the minimum energy required to remove a delocalized electron from the surface of the metal The work function satisfies 15quot 2 hr fl where fl is the threshold frequency for the metal The maximum kinetic energy of an ejected electron is then rmm h Kinetic energy is positive so we must have 3quot u for the photoelectric effect to occur 0 PRINCIPAL QUANTUM NUMBER AND ANGULAR MOMENTUM QUANTUM NUMBER The principal quantum number n and angular momentum quantum number tell you key facts about an electron subshell The principal quantum number n and angular momentum quantum number tell you key facts about an electron subshell For example n tells you how far from the nucleus the electrons in the subshell are Electrons in subshells with higher n are farther from the nucleus and more likely to participate in chemical reactions The electrons in an atom that have the highest n are called valence electrons l tells you how many orbitals are in a subshell Since each electron orbital can hold two electrons the number of orbitals in a subshell tells you how many electrons the subshell can hold l tells you the shape of the orbitals in the subshell The orbital in an I 0 subshell has the simplest possible shape a sphere and orbitals in subshells with higher I have increasingly complicated shapes Orbitals with more complicated shapes are not as good as screening outer electrons from the attraction of the nucleus n and I together tell you the energy of the electrons in the subshell Roughly speaking the energy increases with both n and For example an electron in the 3d n3l2 subshell has a higher energy than an electron in the 2p n2 l1 subshell More precise statements can be made using the n l rules 0 SCREENING EFFICACY OF ATOMIC ORBITALS How well other electrons screen a given electron follows these general rules 1 Electrons in inner shells screen more effectively than electrons in the same shell Electrons in shells with lower n spend more time close to the nucleus which means they are more likely to be between the given electron and the nucleus where the repulsive outward force they exert cancels some of the attractive inward force from the nucleus For example in this case an electron in a 2s or2p orbital for which n2 will screen better than an electron in a 4s or 4p orbital for which n4 2 Electrons in orbitals with lower l screen more effectively The screening effectiveness of orbitals goes like this Sgtpgtdgtf Electrons in orbitals with lower I such as s and p electrons spend more time close to the nucleus than electrons in orbitals with higher I such as d and f electrons for example in this case an electron in a 2s orbital for which l0 will screen better than an electron in a 2p orbital for which l1 3 Electrons in the same subshell screen each other very little Electrons in the same subshell are not very likely to be between each other and the nucleus so they provide very little screening to each other For example in this case the electron in a 4p orbital will get very little screening from an electron in another 4p orbital O IONIZATION ENERGYIONIZATION ENERGY AND ELECTRON AFFINITYELECTRON ATTACHMENT A reaction in which a neutral atom loses an outer electron is called an ionization reaction A reaction in which a neutral atom loses an outer electron is called an ionization reaction Nag gt Na ge AEENa4958kJmol Nag gt Na2 ge AEE2Na4562kJmol Ionization reactions always absorb energy and the amount of energy absorbed is called ionization energy symbol IE Cations may also undergo ionization reactions with energy changes called the element39s 2nd 3rd et cetera ionization energies A reaction in which a neutral atom gains an outer electron is called an electron attachment reaction Fge gt Fg AE EAF328kJmol Fg 9 Fg AE lEF16810kJmol Electron attachment reactions normally release energy The amount of energy released when an electron attaches to a neutral atom is called the electron affinity symbol EA If an electron attaches to a cation the attachment reaction is the reverse of an ionization reaction and the energy released is equal to the appropriate ionization energy Note it39s important to think carefully about the sign of energy changes during ionization and electron attachment reactions Do not rely on the signs of ionization energies and electron affinities listed in Periodic Tables and other references because sign conventions may differ Instead use your physical intuition that pulling an electron away from the attraction of a nucleus ionization will require energy and conversely allowing an electron to respond to the attraction of a nucleus electron attachment will usually release energy 0 RATE LAW A rate law is an equation that tells you how the rate of a chemical reaction depends on the concentrations of its reactants Rate laws usually look like this matrix ital writer in A mm rmwth renter murder m B This equation tells you the rate of reaction is proportional to the molarity of A squared times the molarity of B cubed The proportionality constant is called the rate constant and the power to which each concentration is raised is called the reaction order for that reactant The sum of all the reaction orders is called the overall reaction order Note when an exponent is 1 we don39t write it That means that when a rate law has the concentration of a reactant with no power the reaction is first order in that reactant O PRESSURE AND VOLUME CHANGEBOYLE39S LAW Boyle39s Law says that the volume of gas is inversely proportional to the pressure as long as the temperature doesn39t change 0 ELECTROSTATIC POTENTIAL ENERGY First the potential energy of a pair of charges is positive if they are like charges and negative if they are unlike charges o Notice that this means the potential energy of a pair of like charges is always higher than the potential energy of a pair of unlike charges H d E like g 9 91 changes unlike r 1H a 39 charges potential energy U I When like charges get closer potential energy goes up Whe n unlike charges get closer potential energy goes down Second the magnitude of the potential energy decreases with the separation between the charges see sketch at right That is the potential energy of a pair of unlike charges gets less negative as the separation between them increases and the potential energy of a pair of like charges gets less positive That means when the pair gets very far apart the potential energy approaches zero for both like and unlike charges o For example the potential energy of a 1 charge and a 2 charge becomes more positive if they get closer o On the other hand the potential energy of a 1 charge and a 2 charge gets more negative if they get closer Finally the magnitude of the potential energy grows with the product of the charges That is the potential energy of a pair of unlike charges gets more negative as the product of the charges increases and the potential energy of a pair of like charges gets more positive o For example the potential energy of a 1 and 2 charge is more positive than the potential energy of a 1 and 1 charge separated by the same distance o On the other hand the potential energy of a 1 charge and a 2 charge is more negative than the potential energy of a 1 charge and a 1 separated by the same distance 0 THE LENGTH AND STRENGTH OR EQUIVALENT ENERGY OF A COVALENT CHEMICAL BOND The length and strength or equivalent energy of a covalent chemical bond is determined by the concentration of negative electric charge between the nuclei The more concentrated the negative charge in this region the more powerful are the electric forces that pull the nuclei toward each other and therefore the stronger and shorter the chemical bond This general idea implies two specific rules that will let you solve this problem o For the same atoms more shared electrons mean a stronger and shorter chemical bond That39s because more shared electrons pack more negative charge into the same space between the nuclei For example as the number of valence electrons shared by a carbon and oxygen atom increases the bond between them gets shorter and stronger Bond CO single b ond CO double bond CO triple bo nd shared elect rons bond leng th pm 143 longes t 123 113 sharia st bond energ Y kJnK 358 Weakes t 799 1072 strange st For the same number of shared electrons smaller atoms mean a stronger and shorter chemical bond That39s because reducing the distance between the nuclei concentrates the same amount of negative charge into a smaller space For example the single bond between a hydrogen atom and a halogen atom gets longer and weaker as we go down Group 7A from fluorine to iodine Bond I F39 71pnn IC 99pnn radius of halogen atom bond lengt h pm 92 snortes t 127 bond energy Bglnu 567 stronges t 431 1 14pm 141 366 H I 133 161 299 m p anges weees 1 As the halogen atoms get bigger the bonds with hydrogen get longer and weaker Now the highlighted bonds in the table of compounds you39ve been given in this problem are all single bonds between carbon and an atom of an element from Group 7A The only difference between them will be the size of the Group 7A atom Therefore the second rule above tells you how to order the compounds by bond length and bond energy o The smallest atoms will form the shortest bond with the highest bond energy and the largest atom will form the longest bond with the lowest bond energy o You39ll also need to remember the fact that the size of atoms increases as we go down a group of the Periodic Table 0 LATTICE ENERGY All of the compounds in the table are binary ionic compounds held together in the solid state by the attractive electrostatic forces between the cations and anions from which they39re made The stronger these forces the bigger the lattice energy will be We can use Coulomb39s Law to help estimate the strength of the attractive forces holding each ionic compound together and therefore the size of its lattice energy Coulomb39s Law tells us that the attractive force between a cation with charge q and an anion with charge q is directly proportional to the magnitude of the charges and inversely proportional to the square of the distance r between the ions Here s that fact as an equation The Fklqq lrA2 k is a constant of proportionality There are therefore two ways in which the attractive forces between cations and anions could be stronger and therefore lattice energy be bigger o A compound could be made from ions with charges of greater magnitude o A compound could be made from ions with a smaller radius A difference in magnitude of charge is usually more important than a difference in radius because ions do not vary much in size D LUCK lllNl Y UR EXAM
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