Rates of Reactions October 2015. 1) What is ALWAYS represented by the slope of the tangent to a graph of concentration vs. time for a reaction? a)The.

Rates of ReactionsOctober 2015

1) What is ALWAYS represented by the slope of the tangent to a graph of concentration vs. time for a reaction?

a) The activation energy for the reactionb) The enthalpy change for the reactionc) The initial rate of the reactiond) The average rate of the reactione) The instantaneous rate of the reaction

2) Which statement is false?

a) ΔHforward is a positive quantity

b) ΔHreverse is a negative quantity

c) ΔHreverse is equal in magnitude to ΔHforward

d) Ea reverse is equal to Ea forward

e) Ea reverse is less than Eaforward

3) Which of the following statements is false?

a) D is a reaction intermediateb) The overall reaction is

endothermicc) EG is the fastest stepd) CE is the rate determining

stepe) The reaction has a 3-step

mechanism

4) In the following diagram, the letter which represents the position of the activated complex is:

a) Ab) Bc) Cd) De) E

5) Which statement regarding the potential energy diagram below is false?

a) The Ea for the uncatalyzed reaction in the forward direction is +30 kJ

b) ΔH for the uncatalyzed reverse reaction is +20 kJ

c) The potential energy of the activated complex for the catalyzed reaction is +50 kJ

d) The catalyst lowers the activation energy of the forward and reverse reactions by 20 kJ

e) Ea the uncatalyzed reverse reaction is +70 kJ

6) The theoretical effect of an increase in the initial concentration of a reactant can be explained in terms of collision theory because it affects

I. the collision geometry involved in the reactionII. the total number of collisions that occurIII. the fraction of collisions that are effectiveIV. the required activation energy for a reaction

a. both I and IVb. I, II and III are truec. both II and III d. both III and IVe. II only

7) The theoretical effect of a catalyst can be explained in terms of collision theory because it affects

I. the collision geometry involved in the reaction

II. the total number of collisions that occurIII. the fraction of collisions that are effectiveIV. the required activation energy for a

reaction

a. both I and IVb. I, II and III are truec. both II and III d. both III and IVe. II only

8) The theoretical effect of an increase in temperature can be explained in terms of collision theory because it affects

I. the collision geometry involved in the reactionII. the total number of collisions that occurIII. the fraction of collisions that are effectiveIV. the required activation energy for a reaction

a. both I and IVb. I, II and III are truec. both II and III d. both III and IVe. II only

9) For a reaction having ΔH of -42kJ and an activation energy of +63kJ, the activation energy for the reverse reaction is:

a) 105 kJb) -105 kJc) -63 kJd) 21 kJe) -21 kJ

10) If the temperature is increased, how will the resulting graph differ from the one below?

a) Both areas I and II will increaseb) Both areas I and II will

decreasec) Area I will increase and area II

will decreased) Area I will decrease and area II

will increasee) Both areas I and II will remain

the same

11) If a catalyst is added, what will happen to the activation energy?

a) It will remain the sameb) It will shift to the rightc) It will shift to the leftd) No prediction can be made

12) If the concentration of one of the reactants is increased, what will happen to areas I and II?

a) Both area I and area II will increase by the same factor

b) Area I will increase, area II will not

c) Area II will increase, area I will not

d) Area II will increase, area I will decrease

13) If Ea1 represents the activation energy of reaction 1 and Ea2 represents the activation energy of reaction 2, which statement is true when the temperature of both reactions increases?

a)Reaction 1 will still be slower than reaction 2b) Reaction 2 will become faster than reaction 1c) Reaction 1 will increase in rate by a greater factor than reaction 2d) Reaction 2 will increase in rate by a greater factor than reaction 1

14) What will happen to the height of the curve when the temperature increases?

a) It will remain the sameb) It will increasec) It will decreased) It is difficult to predict

15) Which of the following statements is true if A is a reactant?a) The [A] vs time graph is a straight line if A is first order b) If A is zero-order, the [A] vs time graph is a horizontal linec) The 1/t vs [A]2 graph is a straight line if A is second orderd) If the rate vs [A] graph is an upward curve, then A must be second

order