02 Notes - Rate Laws

02 Notes - Rate Laws - If you change the concentration...

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Aim: What are rate laws and what information to they provide? QQ: Explain how a catalyst works. Do Now: How does the concentration of the reactants affect the rate (speed) of a reaction? Rate Law: describes how the rate of reaction varies with the concentrations of various species, usually reactants, in the system. Rate laws must be determined experimentally ! X + Y Z rate = k [X] a [Y] b k = rate constant (different for each reaction) [X], [Y] = concentrations of X and Y (in molar) a and b = order of reaction according to that reactant Practice: What is the generic rate law for the reaction: F 2 (g)+ 2ClO(g) → 2FClO 2 (g) What are the values of a and b? What is the value of k? What will the rate be if I change the concentration of the reactants? Exp Initial [F 2 ] Initial [ClO] Initial Rate (M/s) 1 0.10 M 0.010 M 0.0012 2 0.20 M 0.010 M 0.0024 3 0.10 M 0.040 M 0.0048 What are the values of a and b?
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Unformatted text preview: If you change the concentration and… Example Order Nothing happens to the rate Concentration 2x, rate remains the same 0 The rate changes by the same amount Concentration 2x, rate increases by 2x 1 The rate changes by x 2 Concentration 3x, rate increases by 9x 2 rate = k [F 2 ] a [ClO] b a = 1 and b = 1 overall order = 1 + 1 = 2 rate = k [F 2 ] [ClO] What is the value of k? rate = k [F 2 ] [ClO] 0.0012 = k [0.10] [0.010] k = 1.2 1 M-1 s-1 What would the rate be if… [F 2 ] = 0.30 M, [ClO] = 0.030 M rate = k [F 2 ] [ClO] Rate = 1.2 [0.30] [0.030] Rate = 0.0108 M/s Conclusions: Rate laws are based on the concentration of the reactants Write the general rate equation for a reaction first Use data to determine the order of the reaction, the value of k (rate constant), and to predict what the rate of the reaction would be at other concentrations...
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