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17_kinetics_rates (2)

# Ch3nc ch3cn first order reactions ch3nc ch3cn this

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Unformatted text preview: his reaction at 198.9 oC. 9 11/20/2013 First-Order Reactions ln [A]t = -kt + ln [A]0 • reaction is 1st order because lnP vs time is linear • k is the negative of the slope, 5.1x10-5 s-1 First-Order Reactions A + B Products If 1st order in [A] separate variables 1 integrate ln ln ′ linear relation solve for [A]t 10 11/20/2013 N2O5(g) 2NO2(g) + 1/2O2(g) @318 K N2O5(g) 2NO2(g) + 1/2O2(g) @318 K . 3.1 10 . 3.1 10 -1 -1 11 11/20/2013 Half Life and 1st Order Rate Constant What is time to halve a certain concentration? 1/2 1 2 1 2 2 / 0.693 / Effect of Value of k 12 11/20/2013 Follow Appearance of Products N2O2(g) 2NO(g) 1 2 1 2 2 separate variables ′ integrate 2 2 ′ 0 2 1 N2O2(g) 2NO(g) reactant product 2 1 13 11/20/2013 Second-Order Reactions A + B Products If 2nd order in [A] separate variables 1 integrate 1 1 solve for [A]t ′ 1 linear relation 1 14 11/20/2013 Second-Order Reaction decomposition of NO2 at 300 oC NO2 (g) Time (s) NO (g) + 1/2O2 (g) [NO2], M 0.0 0.01000 50.0 0.00787 100.0 0.00649 200.0 0.00481 300.0 0.00380 NO2(g) NO(g) + 1/2O2(g) 1st order? No linear if 1st order linear if 2nd order 2nd order? Yes linear 15 11/20/2013 1st Order in Reactants, 2nd Order Overall A + B Products Δ solve for , plug into expression for [B] Δ separate variables 16 11/20/2013 1 integrate ′ except when [A]0=[B]0 integrated rate law A + B Products when [A]0=[B]0, problem 28-5 shows that 1 1 1 1 …like simple second order laws 17 11/20/2013 Example 28-6 k1 H+(aq) + OH-(aq) ⇆ H2O(l) k-1 Calculate reaction half life with k1=1.4x1011 dm3 mol-1 s-1, if [H+]0=[OH-]0=0.10 mol dm-3=0.10 M 1 1 1 1 1 half life / 1 / 1 / /2 1.4 10 1 0.10 /2 1 1 7.1 10 71 ps Example 28-6 k1 H+(aq) + OH-(aq) ⇆...
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