#Chem 162-2008 3rd week recitation

#Chem 162-2008 3rd week recitation - CHEMISTRY 162-2007 3rd...

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CHEMISTRY 162-2007 3 rd WEEK RECITATION ANNOUNCEMENTS E-MAIL ATTENDANCE Sign in QUIZ Recitation quiz this week  Wed – Chapter 12.1 – 13.3 Thu – Chapter 12.7 – 13.5 (Mon – Chapter 12.8 – 13.7) Will run late due to quiz.  Quiz will be at end of recitation. Pick up graded quizzes after class next week. Chem 162-2008 3 rd week recitation 1
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PLAN FOR TODAY : CHEMICAL KINETICS Reaction rates Rate laws from experimental data - Initial Rates Method Integrated rate laws - Half-lives Chem 162-2008 3 rd week recitation 2
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FORMULAS C 12 H 22 O 11 + H 2 O ----> C 6 H 12 O 6 + C 6 H 12 O 6 Rate of sucrose disappearance = -(∆ [sucrose])/(∆ time) = -([sucrose f ] - [sucrose i ])/(t f - t i ) aA + bB ----> cC + dD General rate of reaction = -(1/a)(∆[A]/∆t) = -(1/b)(∆[B]/∆t) = (1/c)(∆[C]/∆t) = (1/d)(∆[D]/∆t) Determination of order of reaction through method of initial rates: For a single reactant: Rate 1 = k[A 1 ] m Rate 2 = k[A 2 ] m (Rate 1/Rate 2) = (k[A 1 ] m )/(k[A 2 ] m ) = ([A 1 ]/[A 2 ]) m For two reactants: Rate1 = k[A 1 ] m [B 1 ] n Rate2 = k[A 2 ] m [B 1 ] n (Rate1/Rate2) = (k[A 1 ] m [B 1 ] n )/(k[A 2 ] m [B 1 ] n ) = (A 1 /A 2 ) m Integrated Reaction Differentiated rate law k Order Reaction Rate** RATE LAW*** (y = mx + b) Half-life * units 0 Rate = -(C 2 -C 1 )/(t 2 -t 1 ) Rate = k[C] o =k [C] t = -kt + [C] o t 1/2 = [C] o /2k M 1 s -1 1 Rate = -(C 2 -C 1 )/(t 2 -t 1 ) Rate = k[C] 1 ln[C] t = -kt + ln[C] o t 1/2 = 0.693/k M o s -1 2 Rate = -(C 2 -C 1 )/(t 2 -t 1 ) Rate = k[C] 2 1/[C] t = kt + 1/[C] o t 1/2 = 1/(k[C] o ) M -1 s -1 ** Rate of appearance = +slope; rate of disappearance = -rate of appearance = -slope. *** Differentiated Rate Law may be for more than one component, e.g., Rate = k[C] 1 [D] 2 *Half-lives : For a zero order reaction, each successive half-life is ½ the preceding one. For a first order reaction, each successive half-life is equal to the preceding one. For a second order reaction, each successive half-life is double the preceding one. Arrhenius equation: k = Ae (-Ea/RT) A = frequency factor = combination of steric factor and collisional frequency E a = energy of activation ln k 2 - ln k 1 = (-E a /RT 2 ) - (-E a /RT 1 ) Chem 162-2008 3 rd week recitation 3 ln k = -E a /RT + ln A ln (k 2 /k 1 ) = -(E a /R)[(1/T 2 ) - (1/T 1 )]
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REACTION RATES OF PRODUCTS AND REACTANTS ET: Show that rate of formation of product is the slope, and rate of disappearance of reactant is negative of the slope. 2A + B → 5C + 4D Formation of D 10 X 2 Y 2 Rate of increase of [D] = (Y 2 – Y 1 )/(X 2 – X 1 ) Rate of increase of [D] = slope of line (SOL) Rate of increase of [D] = (10 – 0)/(5 – 0) = 2M/s which is the convention for formation of product Conc (M) X 1 ,Y 1 0,0 time 5 Disappearance of A Rate of increase of [A] = (Y 2 – Y 1 )/(X 2 – X 1 ) Rate of increase of [A] = slope of line (SOL) Rate of increase of [A] = (0 – 5)/(5 – 0) = -1M/s = SOL -Rate of increase of [A] = -slope of line = -(-1M/s) Rate of decrease of [A] = -slope of line = +1M/s 5 X 1 Y 1 Conc (M) 0,0 time 5 X 2 ,Y 2 Rate of formation of product is the slope.
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#Chem 162-2008 3rd week recitation - CHEMISTRY 162-2007 3rd...

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