9. Questions 9-10 refer to the following information. 2 NO(g) + Cl2(g) 2 NOCl(g)
ID: 1075161 • Letter: 9
Question
9. Questions 9-10 refer to the following information. 2 NO(g) + Cl2(g) 2 NOCl(g) Consider the reaction mechanism for the reaction represented above. NO(g) N0(g) C12(g) NOC12(g) NOC12(g) 2NOCI(g) fast equilibrium step slow step + + Which of the following statements is true? (A) Step 1 represents a unimolecular reaction. (B) Increasing the concentration of the Cl2 will decrease the overall rate of the reaction. (C) The addition of a catalyst to the equilibrium step of the reaction would increase the rate of the reaction. (D) The rate law that is consistent with the mechanism is rate-kNOF[C12] AP Chem Exam 2013 MC#24 10. The reaction is exothermic. Which of the following statements would provide justification for the (A) There are fewer moles of product than reactant so the potential energy of the reaction must (B) The bond energy of the products is greater than the bond energy of the reactants; therefore (C) The decrease in volume of the substances in the reaction from 3 mol to 2 mol of gas must (D) Any reaction with a slower second step in the mechanism must be exothermic since the change in enthalpy? decrease because there are fewer covalent bonds in the products. the bone n he resesnroduct than i onsumedin the hreaking of accompanied by an increase in temperature. second step must have a greater activation energy than the first.Explanation / Answer
Answer 9):
Statement A) is a false statement because uimolecular reaction involes only single reactant. However, in given reaction two different reactants (NO and Cl2) are used.
Statement B) is a false statement because increase in the concentration of the reactant (Cl2) increase the overall rate of the reaction since rate is directly proportional to the concentration of the reactants.
Statement C) is a false statement because a catalyst speeds up the forward and backward reaction to the same rate and adding a catalyst does not change the relative rates of the two reactions, it cannot affect the position of equilibrium. According to Le Chatelier's principle "The Equilibrium Law" states that when a system experiences a disturbance, it will restore a new equilibrium state.
Statement D) is a true statement because rate law is the expression relating the rate of reaction with concentration of the reactants i.e. NO and Cl2. The constant of proportionality ‘k’ is known as rate constant.
Rate = k [NO]2 [Cl2]
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