Chemical Kinetics and Chemical Equilibrium

Name ______

CHEMICAL KINETICS AND CHEMICAL EQUILIBRIUM

Assume that R = 8.314Jmol-1K-1

1. For the reaction which of the following below is a correct expression for the rate?

2. Assuming that the reaction is first-order in H2 and first-order in I2, which of the following statements is true

3. The reaction is first-order in N2O5. The rate constant is found to be 0.053/s at a certain temperature. If initially the concentration of N2O5 is 1M and the concentrations of NO3 and NO2 are zero. What would you predict the concentration of the N2O5 to be after 3 seconds?

4. What is the integrated rate law for the concentration of a reactant A when the reaction is second order in A?

5. A plot of ln(Rate Constant) versus 1/Temperature for the following first-order reaction:

gives a straight line graph of slope = -30189K and an intercept of 29.967. Which of the following answers is correct?

(a) Ea = 30.189 kJ/mol and A=29.967 s-1: (b) Ea = 3631 J/mol and A = 1.03x10-13 s-1

(c) Ea = 3.631 kJ/mol and A = 1.03x1013 s-1 (d) Ea = 251 kJ/mol and A = 1.03x10-13 s-1

(e) Ea = 251 kJ/mol and A = 1.03x1013 s-1

6. Consider the following 3-step mechanism for a reaction

What is the predicted rate law?

7. What is the overall order for the above reaction?

(a) 3/2;

(b) 1;

(d) 0;

(e) none of these?

8. In the reaction in question (6) what would happen to the rate of reaction if I double the concentration of Cl2 and double the concentration of CHCl3?

(a) rate remains the same:

(b) rate quadruples:

(c) rate increases by a factor of 2.83:

(d) the rate doubles:

(e) none of these?

9. Consider the two 1-step elementary reactions, (i) H + I à HI and (ii) NOCl + NOCl à 2NO + Cl2. Let us assume that both reactions have the same activation barrier height, and the same collision frequency factor z. Which reaction would have the fastest rate?

(a) reaction (i)

(b) reaction (ii)

In a reaction A + B à C + D you measure the concentration of [A] and [B] as a function of time. You perform 2 experiments, in one [B]o > [A]o so that the time dependent rate only is measuring the rate’s dependence on [A]t. In this experiment you find that when you plot ln[A]t vs time you get a straight line. In the second experiment [A]o > [B]o meaning that the time dependence of the rate only depends on [B]t so and when you plot 1/[B]t versus time you get a straight line. What is the overall order of reaction?

10. What is the order of reaction with respect to [A]?

(a) 0 (b) 1 (c) 2 (d) 3 (e) 4

11. What is the order of reaction with respect to [B]?

(a) 0 (b) 1 (c) 2 (d) 3 (e) 4

12. What is the overall order of reaction?

(a) 0 (b) 1 (c) 2 (d) 3 (e) 4

Chemical Equilibrium

13. For the general reaction what is the equilibrium constant Kc?

14. What is the equilibrium constant for the following reaction,

15. For which of the following reactions will Kp = Kc?

16. Consider the following reaction:

A reaction mixture at 780oC initially contains [CO]=0.5M and [H2]=1M. At equilibrium the CO concentration is found to be 0.15M. What is the equilibrium constant for the reaction?

(a) 26 (b) 0.385 (c) 3.59 (d) 0.278 (e) 6.67

17. Consider the following reaction . A reaction mixture contains , is the reaction mixture at equilibrium and if not in which direction will it proceed?

(a) yes, will not change

(b) no, will move toward the right

18. Consider the following reaction of nitrogen and hydrogen to make ammonia occurring inside a piston, equilibrium is established and the concentrations of the reactants and product measured. You then push the piston down to increase the pressure of the gases and decrease the volume, what happens to the equilibrium?

(a) the equilibrium shifts right toward product

(b) the equilibrium shifts left toward reactants

(c) there is no change in the concentration of reactants or products

19. Consider the reaction

the reaction is known to be exothermic. The equilibrium concentrations of the H2, and I2 and HI are measured at 1000K. The temperature of the reaction vessel is changed to 800K. What happens to the reaction equilibrium, does it

(a) shift left

(b) shift right

20. Consider the following observations about the reaction

Is this reaction

(a) exothermic, (b) endothermic, (c) neither?

The reaction 2 SO2(g) + O2(g) 2 SO3(g) with ΔH° = -198 kJ at equilibrium. How will each of the following changes affect the equilibrium concentrations of each gas once equilibrium is re-established?

21. Adding more O2 to the container

(a) Equilibrium shifts left

(b) Equilibrium shifts right

22. Condensing and removing SO3

(a) Equilibrium shifts left

(b) Equilibrium shifts right

23. Compressing the gases

(a) Equilibrium shifts left

(b) Equilibrium shifts right

24. Cooling the container

(a) Equilibrium shifts left

(b) Equilibrium shifts right

25. Doubling the volume of the container

(a) Equilibrium shifts left

(b) Equilibrium shifts right

26. Warming the mixture

(a) Equilibrium shifts left

(b) Equilibrium shifts right

27. Adding the inert gas helium to the container

(a) Equilibrium shifts left

(b) Equilibrium shifts right

28. Adding a catalyst to the mixture

(a) Equilibrium shifts left

(b) Equilibrium shifts right

29. In a sealed piston the following reaction in conducted , what change will affect the equilibrium constant?

(a) Increasing the amount of CO2(g)

(b) Decreasing the amount of C(s)

(d) Increasing the temperature of the reaction

(e) None of the above

30. Consider the following reaction

In an equilibrium mixture [COF2]=0.255M and [CF4]=0.118M what is [CO2]?

(a) 4.32M (b) 1.10M (c) 0.55M (d) 2.16M (e) 1.08M

LONG QUESTIONS (10 POINTS EACH) (attach sheets showing working)

31. For the following reaction mechanism,

(a) write out the overall reaction (2 points)

(b) what is the reactive intermediate? (1 points)

32. Consider again the reaction . At 25oC the mixture initially contains .

(a) Find the equilibrium partial pressures of I2, Cl2 and ICl at this temperature. (6 points)

(b) what will Kc be at this temperature? (4 points)