Practice Midterm Sol

Practice Midterm Sol - 1 1. (4 marks) Circle the correct...

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1 1. (4 marks) Circle the correct answer. a) (1 mark) If reactant molecules collide with energy greater than the activation energy, they change into product molecules. True False b) (1 mark) The activation energy of a reaction depends on the temperature of the reaction. True False c) (1 marks) If the half-life of a reaction depends on the concentration of the reactant, then the reaction cannot be order. Zero First Second Third e) (1 mark) For a second order reaction, the correct units for the rate constant, k, is i) s -1 ii) M -1 s -1 iii) M -2 s -1 iv) M -3 s -1 v) None of the above 2. a) (3 marks) If two reactions have identical activation energies, does this mean the rate constant will also be identical if the reactions are run at the same temperature? Explain your answer. No, because A (the pre-exponential factor) can be different for the two reactions (k=Ae -Ea/RT ) b) (5 marks) The reaction between Cl (g) and HBr (g) has an overall enthalpy change of –66 kJ and an activation energy of 7 kJ. Sketch a qualitatively correct reaction profile and determine the activation energy for the reverse reaction. Cl (g) + HBr (g) HCl (g) + Br (g) Δ E = -66 kJ, E a (forward) = 7 kJ, E a (reverse) = (66+7) kJ = 73 kJ Potential energy Reaction progress reactants Δ H = 66 kJ/mol E a (forward) = 7 kJ E a (reverse) = 73 kJ
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Practice Midterm Sol - 1 1. (4 marks) Circle the correct...

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