Honors Colloquium CHEM 122
Honors Colloquium CHEM 122 CHEM 122
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This 6 page Class Notes was uploaded by Dr. Drew Flatley on Friday October 30, 2015. The Class Notes belongs to CHEM 122 at University of Massachusetts taught by Staff in Fall. Since its upload, it has received 15 views. For similar materials see /class/232358/chem-122-university-of-massachusetts in Chemistry at University of Massachusetts.
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Date Created: 10/30/15
42605 Assigning Oxidation Numbers This is a more complete set of rules than your text book It always works Use these rules in order The sum of all oxidation numbers of all elements 2 charge on substance Oxidation Number Examples 1 l Atoms in their elemental state 2 0 Fe H2 02 I 2 I Monatomic ions 2 charge F Nat 1363 IN COMPOUNDS 2A Fluorine Oxygen Try these soz HClO4 03 PC15 N02 so NO3391 Noz 1 C1F3 NaH H202 12 The Initial Rate Method Points I looked for when grading What is the initial Rate p t How is it determined How are the orders for each reactant determined 935 How is k determined The Initial Rate Method is a procedure used to determine the rate law for a chemical reaction It consists of running a series of experiments where the initial concentration of each reactant is systematically changed and the concentration of one of the reactants or products is followed as a function of time All concentrations are related by the stoichiometry only need to follow one The initial rate of the reaction is the instantaneous rate at the very beginning of the reaction and is determined for each experiment by nding the slope of the line tangent to the curve of a concentration vs time graph measured at t 0 A Initial Rate 7 Slope of tangent line art 0 time From the generalized rate law Rate kAquotBy the order with respect to each reactant can be determined because the ratio of the initial rates for two different experiments is equal to the ratios of the initial concentrations raised to their orders X y A AL BL Rate Rate By systematically varying the initial concentrations of A and B the exponents x y can be determined This can be done by inspection or by taking the logarithm of both sides of the equation and solving for x or y Once the orders are known the rate constant can be found by rst calculating k for each experiment they should be very close to one another Rate AfB3 and then averaging these values Silver Cleaning Recipe Aluminum foil crinkled up Hot water Baking soda 1 teaspoon Table salt 1 teaspoon Glass bowl REDOX REACTION OXIDATION 2 Als 6 OH aq 7gt A1203s 3 H201 6 e REDUCTION Ag2Ss 2 H201 2 e7 7gt 2 Ags HZSaq 2 OH aq 3 Ag2Ss 2 Als 3 H201 7gt 6 Ags 3 H28aq Ale3s HalfLife The time it takes for a reactant concentration to decrease to 12 of its value t12 What fraction of reactant remains after 2 halflife periods 1 0 2 18 3 14 4 12 5 24 Order HalfLife Zero t12 AL2k Decreases as rxn proceeds First t12 ln 2k Constant throughout rxn Second t1 2 1 A0 k Increases as rxn proceeds Whalis the Order with respect to H202 o 1 2 3 mm a m me E 1 WWW g mm m game I 7 mlezxi 131 mm H z mm 0 zlz m new mu ounzs 1 names 3 a sun mm 1 zoan asau ma mmmmmm W m The Arrhenius Equation Rate Constant depends upon Orientation Energy of Activation and Temperature k A eEaRT A Frequency Factor e39EaRT Collisions with correct Orientation Fraction of molecules with enough Energy to react at given Temperature in Kelvin Linear Form Ink EaR 1T lnA y m X b TwoPoint Form In k2 39E3 1 1 k1 R T2 T1