CHEM 1120 Edition 1nd Lecture 8 Outline of Last Lecture I Arrhenius Equation a How do we know it is true II Reaction Mechanisms a Elementary step b Molecularity Outline of Current Lecture I Catalysis a Catalyst b Homogeneous vs Heterogeneous catalysis c Enzymes II Intro to Chapter 21 Nuclear Chemistry a Chemical vs Nuclear Reactions III Radioactivity a Types of Emissions b Balancing Nuclear Equations Current Lecture I Catalysis a Catalyst a substance that increases the rate of a chemical reaction without undergoing permanent chemical change These 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 II III b Ex Decomposition of H2O2 i Add iodide goes faster why ii Why Different mechanism iii Intermediate appears and disappears in beaker never put it in iv Catalyst put it in and take it out you have control c Why is the 2 step mechanism faster i 2 small energy barriers are easier to surmount than one large barrier d Homogeneous vs heterogeneous catalysis i Homogeneous catalyst and reactants in the same phase ii Heterogeneous catalyst and reactants in different phases e Catalytic converter found in the exhaust manifold of an automobile i Catalyst converts hydrocarbons and nitrogen oxides into carbon dioxide water and Nitrogen gas ii Heterogeneous catalysis f Enzymes biological catalysts most are large proteins i Substrate enzyme enzyme substrate complex ii Enzyme substrate complex enzyme products iii Lock and key model enzyme and substrate match up Intro to Chapter 21 Nuclear Chemistry a Alchemy change something cheap into something expensive go from one element to another b Chemical reactions one substance converted to another atoms never change identity small changes in energy no measurable changes in mass c Nuclear reactions atoms of one element typically convert into atoms of another element large changes in energy and measurable changes in mass Radioactivity a Unstable radius exhibits radioactivity spontaneously disintegrates or decays i Protons and neutrons elementary particles that make up nucleus are collectively called nucleons ii Nuclide nucleus with a particular composition has a specific atomic number and mass number iii Isotopes same number of protons different numbers of neutrons iv Radioactivity or radioactive decay spontaneous emission of particles or radiation from atomic nuclei v Nucleon a proton or neutron vi Radionuclide nuclide that is radioactive vii Radioisotope atom containing a radionuclide b Review of nucleus i nucleus comprised of 2 nucleons protons and neutrons ii Number of protons is atomic number iii Number of protons and neutrons together is effectively the mass of the atom c Types of Emissions i Radioactive decay when a nuclide of one element spontaneously decays into a nuclide of a different element ii 3 common types alpha beta and gamma iii Alpha Charge 2 Relative penetrating power 1 nature of radiation He nuclei iv Beta Charge 1 Penetrating power 100 nature electrons v Gamma Charge 0 penetrating power 10000 nature high energy protons d Balancing Nuclear Equations i When a nuclide decays forms a nuclide of lower energy and excess energy carried off by the emitted radiation 1 Decaying or reactant nuclide is called parent 2 Product nuclide is called daughter ii Ex Alpha decay 1 Ra Rn He iii Beta decay 1 Reactant gains a proton electron iv Positron decay involves the emission of a positron from the nucleus 1 Positron is anti particle of electron 2 Reactant loses a proton electron v Electron capture occurs when nucleus of an atom draws in an electron from an orbital of the lowest energy level vi Gamma emission involves the radiation of high energy gamma photons from an excited nucleus vii