General Chemistry CHM 115
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Ms. Jayde Murray
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This 0 page Class Notes was uploaded by Ms. Jayde Murray on Sunday November 1, 2015. The Class Notes belongs to CHM 115 at Indiana University Purdue University - Fort Wayne taught by Staff in Fall. Since its upload, it has received 13 views. For similar materials see /class/233566/chm-115-indiana-university-purdue-university-fort-wayne in Chemistry at Indiana University Purdue University - Fort Wayne.
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Date Created: 11/01/15
ValenceShell ElectronPair Repulsion Section 101 How to predict the shape of molecules 3D arrangement of atoms in a molecule ls H20 linear or bent ls NH3 planar or nonplanar ValenceShell ElectronPair Repulsion Theory VSEPR otoAssumption electron pairs in the valence shell of an atom repel each other Bondingpair bp electrons electrons involved in bonding Lonepair lp electrons electrons not involved in bonding otoMolecule adopts a geometry around the central atom which minimizes the repulsive forces between bondingpair and lonepair electrons Maximize the distance between these bp and lp electrons Arrangement of Electron Pairs Around a Central Atom E Pe Geometry 2 Linear T genal Planar 4 Tetrahedral Arrangement of Electron Pairs Around a Central Atom EPs Geometry T gonal Bipyramidal 6 Octahedral Applying VSEPR 1 Draw the Lewis structure of the molecule 2 Count the number of electron pairs around the central atom Multiple bonds double and triple bonds count as one electron pair 3 Determine the molecular geometry based on the number of lonepair lp and bondingpair bp electrons otoln molecules with both lp and bp electrons the repulsions decrease in the order less favorable Ip Ip gt Ip bp gt bp bp more favorable ie minimize the number of close lp Ip interactions Applying VSEPR Five Electron Pair Example 391 F t 5 regions at electron density around the 3 31 central etem Cl I It i Trigonal Bipyramidal Arrangement Elli quotif of Electron Pairs There are three peeeible structures In Iquot F I we F I fn39t39F I ee F 391 cr F Cr 7 F 7 1 K 43 F F A E C 90 lp lp 0 1 0 90 lp bp 6 3 4 Tshaped Geometry Applying VSEPR Six Electron Pair Example KEF E regime uf electrun de neity around the 4 g fig central aturn Cl Iii tir 1 Octahedral Arrangement of 3 H 139 Electron Pairs There are two pessible structures Iii ill Fax Wall 13 39RVF F 1 F I A E Geometry Square Planar Summary of ElectronPair Arrangements and Geometries Figures 102 103 108 Total of of of Electron Bonding Lone ElectronPair Molecular Pairs Pairs Pairs Arrangement Geometry Example 2 2 0 linear linear 3 3 0 trigonal planar trigonal planar 3 2 1 trigonal planar bent 4 4 0 tetrahedral tetrahedral 4 3 1 tetrahedral trigonal pyramidal 4 2 2 tetrahedral bent 5 5 0 trigonal trigonal bipyramidal 5 4 1 trigonal see saw 5 3 2 trigonal Tshaped 5 2 3 39trigonal 39 linear 6 6 0 octahedral octahedral 6 5 1 octahedral square pyramidal 6 4 2 octahedral square planar Summary of Selected Molecular Geometries A bent I I axe393 a l X X 1quot A a K 339 lt7 X trigclnal pg an dal 939 H l 39 12 A H T shaped H 6 9n39 39 K I K 12 45 EVA seesaw K K lt K J ff A k x XH 90 l 9039 H H 439 K33 square pmn al square planar 9 lt galKt Dipole Moment and Molecular Geometry Section 102 Dipole Moment 1 a measure of the charge separation in molecules containing atoms of different electronegativities ie the molecule has a side and a side Example HCI EN for H 21 EN for CI 30 otoDipole moment 11 is calculated by u Q 6 r where Q is magnitude of charge and r is distance between charges the unit is a Debye D Polar and NonPolar Molecules Polar molecule Nonpolar molecule Examples H20 C02 302 NH3 Polar and NonPolar Molecules Chara dipole moment a D Magnitude of the Dipole Moment oz The larger the difference in EN of the two atoms the larger the dipole moment Example H F AEN40 2119 u1920 H Cl AEN 30 21 09 u 108 D H Br AEN 28 21 07 u 078 D Which has the largest dipole moment H2O C02 302 NH3 Properties of Gases Section 51 The following elements and compounds are considered gases under normal conditions of temperature and pressure Elements Compounds H2 N2 02 F2 and C2 HF HCI HBr HI CO NO He Ne Ar Kr Xe Rn 002 N02 N20 802 H28 NH3 CH4 C2He CsHs C2H4 Csz Properties of Gases gases assume volume and shape of container gases exert pressure gases are the most compressible state of matter gases mix evenly and completely diffuse readily gases have much lower densities than liquids and solids atoms within a gas molecule are held together by chemical bonds gas molecules are not held together Gas Pressure and Its Measurement Section 51 SI Unit for Pressure Barometer Conversions to Other mHg 1 atm 1 atm 1 atm 1 atm force pressure I area pascal Pa 1 Pa 1 2 1 kg 2 m mus Units of Pressure 1 torr 760 mmHg 760 torr 101325x105 Pa 147 psi 2992 inches of Hg Vacuum Mercury Hg I1 mm Atmospheric Elg Converting Units of Pressure Example The pressure of a gas in a ask is measured to be 1055 mmH using a mercury lled manometer as shown to the right What is this pressure in atmospheres atm and pascals Pa Vacuum 4t proporl iona to gas pressure Gas pressure on mercury sr ace Mercury Gas Laws Section 52 53 ABC Gas Laws Avogadro s Law V 0C 11 P T constant 1 Boyle s Law V CC E n T constant Charles Law V CC T P n constant ABC gas laws give rise to Ideal Gas Equation Voc Avogadro39s Law Section 52 V 1 1 at constant temperature 0 ume 0C m0 es and pressure Standard Temperature and Pressure STP Avogardro s Law 273 K 1 atm Molar Volume Vm of a Gas Boyle39s Law Section 52 Boyle s Law Boyle s Law Calculations P1 Example 380 mL of H2 gas originally at a pressure of 690 mmHg will occupy what volume at a pressure of 10 atm Charles s Law Section 52 Charles s Law Volume 0C Temperature at constant pressure GEO V1 V2 Charles s Law Calculations T1 T2 Example At what temperature does a sample of Ne gas occupy 400 L if initially it contained 100 L at 373 K Combined Gas Law Section 52 l1V1 l2Vz T1 T2 Example At what temperature in C does a sample of 02 gas occupy 400 L at 111 atm if it initially occupied 222 L at 100 atm and 600 C The Ideal Gas Law Section 53 V 0C E V 2 RE WhereR 00821D P moloK PV nRT Example How many moles of C2 gas are present in a 275 mL flask maintained at a temperature of 50 C and a pressure of 425 mmHg Use of the Ideal Gas Law to Find Molecular Weight MVIO of a Gas PVZIIRT n Use of the Ideal Gas Law to Find Molecular Weight MVIO of a Gas Example A 0181 9 sample of a gaseous compound with an empirical formula of CH2 occupies 120 mL at 85 C and 800 mmHg pressure Calculate the molecular weight MW of the compound What is the molecular formula Use of the Ideal Gas Law to Find Density of a Gas PVnRT n dz MW V Use of the Ideal Gas Law to Find Density of a Gas Example What is the density in gL of uranium hexafluoride U F6 MW 352 gmol at 779 mmHg and 620 C Stoichiometry Problems with Gases Section 54 Example 029 reacts with 257 g of Fes according to the following equation 4 Fes 3 029 9 2 Fe203g a How many moles of 029 are required to react with Fes MW 558 gmol b What volume of 029 at STP is required to react with all the Fes Stoichiometry Problems with Gases Cont How many grams of Na2003s MW 106 gmol are needed to prepare enough 0029 to fill a 250mL bulb at a pressure of 738 mmHg and a temperature of 23 C Na2003s 9 Na20s 0029 Wave Nature of Light Section 71 Wave Wave311 gth A J U Wavelength A lambda Frequency v nu fa Electric Field E1 Magnetic Fiaid E otoLight consists of electromagnetic waves fix Wavelength 1 Figure 2 AV 2 C Where c 300 X 108 ms Wave Nature of Light Cont Electromagnetic Radiation E Energy 0 v l Alum Vim Germ PollI Boa Child Foolhlll pitch 1o2 Wavelengthm 042 mm w s 106 1a4 10 2 1 Guam my X my Ullrmminl lnlmmd Mamlawns Rille wlwm m4 l l l Frequency HZ 1020 1015 1016 1014 1012 1010 108 r 2 K mm mclmm m m sun all m mu m 7 Relationships shorter higher greater longer lower lesser Quantum Effects and Photons Section 72 Max Planck s Quantization of Energy ozoWhen solids are heated electromagnetic radiation is emitted and that this energy is dependent on the wavelength ozoCIassical physics assumed that atoms and molecules could emit or absorb any arbitrary amount of radiant energy otoPlanck assumed that energy could only be absorbed or emitted in discrete quantities or quanta otoEnergy E of a single quantum of energy Ezhv where h 663 x 10quotquot4 J s Planck s constant Energy is always emitted or absorbed in wholenumber multiples 1hv 2 hv 3 hv
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