chem week 7 notes!
chem week 7 notes! CHE 106 - M001
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CHE 106 - M001
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This 4 page Class Notes was uploaded by Andrea Scota on Sunday October 18, 2015. The Class Notes belongs to CHE 106 - M001 at Syracuse University taught by R. Doyle in Fall 2015. Since its upload, it has received 34 views. For similar materials see General Chemistry Lecture I in Chemistry at Syracuse University.
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Date Created: 10/18/15
mentioned in class Chem Notes Week 7 TEXTBOOK CHAPTER 5 Calorimetry 55 Calorimetry is the that is determined by measuring the magnitude of temperature change that ow produces using a o The temperature change experienced by an object is determined by 1128 is extensive Molar heat capacity is heat capacity of one mol of substance Cm is intensive 0 Speci c heat quantity of heat transferred q grams of substance temp change 0 Can calculate the quantity of heat a substance loses or gains by using the speci c heat with mass and temperature change Monitoring the temperature of a solution we are seeing the ow of heat between a system and its surroundings 0 qreaction qsolution qreaction Combustion reactions are studied using calorimetry using a bomb calorimeter 0 Heat released is captures by surrounding water to nd the heat of reaction we must know the total heat capacity of the calorimeter Coal 0 qreaction 39CcalX 0 heat transferred AE internal energy Hess s Law 56 0 Whether reaction is carried out in one step of multiple the sum of enthalpy changed associated with individual steps must equal the enthalpy change associated with the one step processes Remember H is a state function so the reaction is the same if performed in 1 step or in many steps Enthalpies of Formation 57 Can use methods discussed to calculate enthalpy changes like enthalpies of vaporization or fusion Enthalpy of formation the formation of a compound from constituents AHf Standard state de ned set of conditions an elements pure form at atmospheric pressure and the temperature of interest usually 25 0C Standard enthalpy change of reaction is enthalpy change when all reactants and products are in standard states AHquot 0 AH AHf By de nition the of formation is the because no formation reaction is needed when the element is already at its standard state Can use Hess s Law and AHf values to calculate the standard enthalpy change for any reaction o 2 means quotsum of n and m are stoichiometric coefficients of relevant chemical equation Foods and Fuels 58 fuel valve of a substance is the energy releases when on gram of any substance is combusted most common fuels are hydrocarbons and fossil fuels natural gas consists of gaseous hydrocarbons petroleum is liquid composed of hundreds of compounds coal is a solid composed of hydrocarbons with high molecular weight renewable energy sources include solar energy wind energy biomass and hydroelectric energy nuclear power doesn t use fossil fuels but causes problems for waste disposal TEXTBOOK CHAPTER 6 Electronic Structure of Atoms The Wave Nature of Light 61 The electronic structure of an atom describes the energies and arrangements of electrons around the atom A lot of what we know about the electronic structure of atoms has come from the analysis of light with matter 0 Light we see with our eyes visible lights is one type of electromagnetic radiation also known as radiant energy because it carries energy through space lt Increasing Frequency v to 391022 1020 10 in16 to 1012 lo 1390S i o 13904 13902 1390 v Hz W i AM Radio welwes 1046 lot mquot2 1010 108 39Icr6 104 102 lo 102 m4 106 108 7mm Mi ccccc ve Long radio waves a 5 Increasing Wavelength A A Visible spectrle l l l 1 400 500 600 700 Increasing Wavelength Ox in mm gt Electromagnetic radiation moves through a vacuum at the 0 Different types of electromagnetic radiation have electric and magnetic components that vary periodically in wavelength and the number of complete cycles that pass a point each second frequency 0 All electromagnetic radiation moves at the speed of light 0 frequency is expressed in cycles per second or Hertz Hz Quantized Energy and Photons 63 0 When solids are heated the wavelength distribution of radiation depends on the temperature red is more hot than yellow or white Plank proposed that energy can me either released or absorbed by atoms in discrete chunks of some minimum size 0 Energy E of a single quantum constant X frequency o h is constant called Planks constant 6626 X 103934Js o matter can emit or absorb energy only at whole number intervals of h o In quantum theory meaning is can have only certain allowed values 0 Quantum of energy is very small so energy changes seem continuous Einstein used Planks quantum theory to explain the photoelectric effect the emission of electrons from metal surfaces when exposed to light 0 F 0 Each photon must have energy to planks constant time frequency of light A certain amount of energy is required for electrons to overcome attracted forces holding them to the metal Line Spectra and the Bohr Model 64 Spectrum produced when radiation from such sources is separated into its component wavelengths polychromatic 0 Continuous spectrum contains all wavelengths if contains only speci c wavelengths its is called a of element caused by radiation emitted by excited hydrogen atoms Rydberg equation explains wavelengths of line spectrum of hydrogen ts O RH 11112 11122 0 7 wavelength RH is Rydberg constant 1096776 X 107 m391 assumes that the prevailing laws of physics aren t sufficient to describe all the aspects of an atom o Postulates say 1 energy levels exist electrons can only exist at certain energy levels 2 in the transition of electrons they drop or jump from energy level to energy level Proposed model of H atom that explains the line spectrum 0 The energy of the electron in an H atom depends on the value of the quantum number n called the principle quantum number that ts the equation E thH 1n2 when n is a whole number integer each number being a different speci c energy level 0 The energy of an atom increases as n increases 0 The electron in an H atom can be in any orbit and the equation shows us the energy it has in each orbit Lowest energy achieved in n1 call the ground state of a hydrogen atom other values of n are excited states Light is emitted when the electron drops from a higherenergy state to lower light is absorbed to excite the electron from low energy state to high one 0 When nin nity the electron is separated from the nucleus and the energy is 0 0 AE Ef E 218 x 10 3918 J 1n2f 1n21 0 AE when nf gt n1 The energy of the photon must equal the difference in energy between the two states The frequency of light emittedabsorbed if such that hv the difference in E of 2 allotted states