CHEM 1120 1nd Edition Lecture 8 Outline of Last Lecture I. Arrhenius Equationa. How do we know it is true?II. Reaction Mechanismsa. Elementary stepb. MolecularityOutline of Current Lecture I. Catalysisa. Catalystb. Homogeneous vs Heterogeneous catalysisc. EnzymesII. Intro to Chapter 21: Nuclear Chemistrya. Chemical vs. Nuclear ReactionsIII. Radioactivitya. Types of Emissionsb. Balancing Nuclear EquationsCurrent LectureI. Catalysisa. Catalyst: a substance that increases the rate of a chemical reaction without undergoing permanent chemical changeThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. Ex. Decomposition of H2O2i. Add iodide, goes faster whyii. Why? Different mechanismiii. Intermediate: appears and disappears in beaker, never put it iniv. Catalyst: put it in and take it out, you have controlc. Why is the 2-step mechanism faster?i. 2 small energy barriers are easier to surmount than one large barrierd. Homogeneous vs heterogeneous catalysisi. Homogeneous: catalyst and reactants in the same phaseii. Heterogeneous: catalyst and reactants in different phasese. Catalytic converter: found in the exhaust manifold of an automobilei. Catalyst converts hydrocarbons and nitrogen oxides into carbon dioxide, water, and Nitrogen gasii. Heterogeneous catalysisf. Enzymes: biological catalysts; most are large proteins i. Substrate + enzyme  enzyme substrate complexii. Enzyme-substrate complex  enzyme + productsiii. Lock and key model: enzyme and substrate match upII. Intro to Chapter 21: Nuclear Chemistrya. Alchemy: change something cheap into something expensive, go from one element to anotherb. Chemical reactions: one substance converted to another, atoms never change identity, small changes in energy, no measurable changes in massc. Nuclear reactions: atoms of one element typically convert into atoms of another element, large changes in energy and measurable changes in massIII. Radioactivitya. Unstable radius exhibits radioactivity: spontaneously disintegrates or decaysi. Protons and neutrons: elementary particles that make up nucleus are collectively called nucleonsii. Nuclide: nucleus with a particular composition, has a specific atomic number and mass numberiii. Isotopes: same number of protons, different numbers of neutronsiv. Radioactivity or radioactive decay: spontaneous emission of particles or radiation from atomic nucleiv. Nucleon: a proton or neutronvi. Radionuclide: nuclide that is radioactivevii. Radioisotope: atom containing a radionuclideb. Review of nucleus i. nucleus comprised of 2 nucleons: protons and neutronsii. Number of protons is atomic numberiii. Number of protons and neutrons together is effectively the mass of the atomc. Types of Emissionsi. Radioactive decay: when a nuclide of one element spontaneously decays into a nuclide of a different elementii. 3 common types: alpha, beta, and gammaiii. Alpha: Charge 2+, Relative penetrating power: 1, nature of radiation: He nucleiiv. Beta: Charge 1-, Penetrating power: 100, nature: electronsv. Gamma: Charge 0, penetrating power: 10000, nature: high energy protonsd. Balancing Nuclear Equationsi. When a nuclide decays, forms a nuclide of lower energy and excess energy carried off by the emitted radiation1. Decaying or reactant nuclide is called parent2. Product nuclide is called daughterii. Ex. Alpha decay1. Ra  Rn + Heiii. Beta decay1. Reactant gains a proton/electroniv. Positron decay- involves the emission of a positron from the nucleus1. Positron is anti-particle of electron2. Reactant loses a proton/electronv. Electron capture: occurs when nucleus of an atom draws in an electron from an orbital of the lowest energy levelvi. Gamma emission: involves the radiation of high energy gamma photons from an excited