Ex1_S08_ans

Ex1_S08_ans - Name _A. Key_ Problem Session _All Chem 114...

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Name __A. Key________________ Problem Session _All Chem 114 Exam 1 Dr. A. H. Martin Total Points = 100 February 8, 2008 Complete calculations must be shown for all problems to receive full credit. (6 ) 1. The Haber process for the formation of ammonia gas takes place according to the equation N 2 + 3H 2 -----> 2 NH 3 . It the rate of the reaction expressed as ∆[N 2 ]/∆t = 3.50x10 -4 , what is the rate of the reaction expressed in terms of H 2 and NH 3 ? ∆[Ν 2 ] Dt = D[H 2 ] 3Dt = - D[NH 3 ] 2Dt (12) 2. Answer the following based on the mechanism below: +*?>+ A + B X (slow) X + C Y (fast) Y + A Z + B (fast) Z + C P (fast) a) Indicate the intermediate(s) in this reaction. __X, Y, Z___________ b) Indicate any catalysts presenting this reaction. ___B____________ c) Give the overall equation for the reaction. _2A + 2C P d) Give the rate law for the reaction. _rate = k[A][B]_________________________ c) What is the effect on the reaction rate if the [A] is doubled, with the concentrations of all the other reactants kept constant? ___it would double___ f) What is the order in C in this reaction? __zero_________ (12) 3. Consider the reaction 2 N 2 O 5 4 NO 2 + O 2 . A kinetic study of this reaction shows the rate law to be rate = k[N 2 O 5 ]. The value of k at 25°C = 1.4x10 -4 sec -1 when the initial concentration of N 2 O 5 = 1.0 M. a) What is the initial half life for this reaction? (Show calculations) For a 1 st order reaction t 1/2 = 0.693/k t 1/2 = 0.693/1.4x10 -4 = 4950 sec b) Will this half life increase decrease or remain the same as the reaction proceeds? Justify your answer. Remain the same – the half life of a 1 st order reaction is constant with time. Note there is no concentration term in the calculation above c) Will the value of k increase, decrease or remain the same as the temperature of the reaction increases? Explain why. Increase
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Ex1_S08_ans - Name _A. Key_ Problem Session _All Chem 114...

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