Question

48. If the conversion of A to B is slow and B to C is fast, what is the rate equation for this reaction? A) Rate = K[(CH3CHCI][H20] B) Rate - K[(CH3)2CHCI] C) Rate = K[(CH3)CH] [H0] D) Rate = {[(CH3)2CH] 49. Which of the following statements about a catalyst is true? A) A catalyst accelerates a reaction by changing the amount of reactant and product at equilibrium B) A catalyst accelerates a reaction by lowering the energy of activation C) A catalyst accelerates a reaction by raising the energy of activation D) A catalyst accelerates a reaction by lowering the equilibrium constant. 50. Which of the following statements about equilibrium is true? A) Equilibrium favors the products when the energy of the products is higher than the energy of the reactants. B) Equilibrium favors the reactants when the energy of the product is lower than the energy of the reactants. C) Equilibrium favors the products when they are less stable than the starting material of a reaction D) Equilibrium favors the products when they are more stable than the starting material of a reaction.

Answer 1

(48) B

explanation-  In a reaction, if step 1 is the slow step and step 2 is the fast step, then the overall reaction rate depends on step 1 because the slow step is always the rate limiting step or the rate determining step. consider a simple reaction, we write its rate as-

A+B→C+D

rate = k[A]¹[B]¹  

now in the question,first step(conversion from A to B is slow), so it will be rate determining step. The rate will be written as-

rate = k[(CH₃)₂CHCl]¹

(49) B

explanation- The main function of a catayst is to lower the activation energy of reaction. Activation Energy means the certain amount of energy that must be possessed by reactant species so that they can convert into desired product. Therefore, by decreasing activation energy, rate of reaction can be fasten.

(50) D

explanation- Compounds that are lower in energy have increased stability. Thus equilibrium favors the products when they are more stable (lower in energy) than the reactants.