problem set 4

# problem set 4 - CHM 114A/C Fall 2007 Pam Marks Preparation...

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CHM 114A/C, Fall 2007 Pam Marks Preparation for Exam 4 Chapters 14, 15, 19 and 20 Potentially useful information: K = ºC + 273.15 Avogadro’s Number = 6.022 x 10 23 particles/mole E = q + w H ° rxn = n H f ° (products) - n H f ° (reactants) q = ( Sp. Heat) × m × T (Specific Heat water = 4.184 J/g ° C) 2 2 8 34 18 1 1 ( ) (De Broglie's Eq.) υ Constants: 3.00 10 / 6.63 10 2.18 10 photon H i f H c v λ hc E hv E R n n h m c x m s h x J s R x J λ - - = = = ∆ = - = = = = ( 1.86 / ) ( 0.52 / ) o f f f o b b b T iK m K C m T iK m K C m = = = = Zero order: - Δ [A]/ Δ t = k, [A] = [A] o - kt, t ½ = [A] o /2k First order: - Δ [A]/ Δ t = k[A], ln[A] = ln[A] o - kt, t ½ = 0.693/k Second order: - Δ [A]/ Δ t = k[A] 2 , [A] -1 = [A] o -1 + kt, t ½ = 1/k[A] o Δ H ° = E a,f - E a,r k = Ae -Ea/RT lnk = - a E RT + ln A K p = K c (RT) Δ n(gas) R = 8.314 J/mol K Δ S vap = Δ H vap /T boil , Δ S fus = Δ H fus /T melt Δ S ° = Σ nS ° products - Σ nS ° reactants Δ H ° = Σ n Δ H ° f (products) - Σ n Δ H ° f (reactants) Δ G ° = Σ n Δ G ° f (products) - Σ n Δ G ° f (reactants) Δ G = Δ H - T Δ S, Δ G ° = Δ H ° - T Δ S ° Δ G = Δ G ° + RT ln Q Δ G ° = -RT ln K E ° rxn =E ° cell = E ° ox + E ° red ΔG ° = - n F E ° ; ΔG= - n F E 1 1 2 2 1 1 2 2 1 2 2 1 0.08206 / PV PV n T n T R L atm K mol PV nRT r MM r MM = = = = 2 3 1 2 2 KE mv kT = =

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Chapter 14: Kinetics (Omit 14.6) 1. Describe reaction rate in terms of the change in concentration of a reactant or product per change in time. Describe the relative rates of disappearance of reactants or appearance of products for a given reaction. i) Consider the following gas reaction: The average rate of disappearance of N 2 O 4 is determined to 3.0 × 10 -4 M/s at 10 min interval. What is the average rate of appearance of NO 2 for the same interval? a) 1.5 × 10 -4 M/s b) 3.0 × 10 -4 M/s c) 4.5 × 10 -4 M/s c) 6.0 × 10 -4 M/s e) 7.5 × 10 -4 M/s 2. Given a rate law, determine the order with respect to each reactant or product, and the overall order. 3. Determine the rate law for a reaction when given values of initial concentrations and initial rates. i) The following rate data were obtained at 25 o C for the given reaction. What is the rate-law expression for this reaction: Cr(H 2 O) 6 3+ + SCN - Cr(H 2 O) 5 NCS 2 + + H 2 O Exp. [Cr(H 2 O) 6 3+ ] [SCN - ] initial rate (M/sec) 1 1.0 x 10 -4 1.0 x 10 -1 2.0 x 10 -11 2 1.0 x 10 -4 2.0 x 10 -1 4.0 x 10 -11 3 2.0 x 10 -4 1.0 x 10 -1 8.0 x 10 -11 a) rate = k[Cr(H 2 O) 6 3+ ] [SCN - ] b) rate = k[SCN - ] c) rate = k[Cr(H 2 O) 6 3+ ] d) rate = k[Cr(H 2 O) 6 3+ ] 2 [SCN - ] 4. Use integrated rate laws to calculate: time, concentration of reactant after time t, percentage or fraction of reactant that remains after a given time. Also define half-life, and do 1 st -order 1.2-life problems. i) (Half life time from k for 1
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problem set 4 - CHM 114A/C Fall 2007 Pam Marks Preparation...

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