Name:______________

Chemistry 12 Final Exam:

Written response. All answers must be to correct SigFigs and include Units

Fill in the missing word(s) using the space provided (8 marks)

1. The minimum amount of energy required to overcome the energy barrier in a chemical reaction is the ___energy of activation_____.

2. An activated complex is a chemical species that is (Stable/ unstable ) _unstable__ and has (High /Low)____________ PE

3. What describes the energy of colliding particles as reacting molecules approach each other? KE is (increasing/decreasing) ______________ and PE is (increasing/decreasing)_____________________.

4. A substance that increases the rate of a chemical reaction and may be recovered unchanged at the end of the reaction is a(n)_______Catalyst________.

5. A chemical reaction that gives off energy is __Exothermic____ and has a (positive/negative)____________ Δ H

6. A student wishes to monitor the rate of the following reaction:

CaCO2(s) + 2HCl(aq) CaCl(aq) + CO2(g) + H20(l)

Identify two different properties that could be used to monitor the rate of the reaction. Describe and explain the changes that would occur. (2 marks)

Property:__mass of CaCO3______

Change and Explanation: weigh CaCO3 before experiment and go until all used up, calc. rate as mass loss CaCO3 per unit time

Property:__vol CO2 __________ Change and Explanation: use a eudiometer to record the volume of CO2 produced over unit time

7.

a) Complete step 2 (2 marks)b) Define the term reaction intermediate (2 marks)c) Identify a reaction intermediate in the above reaction (1 mark)

8. Using collision theory, give two reasons why an increase in temperature would cause an increase in reaction rate. (2marks)

i) _____________________________________ _____________________________________

ii) __________________________________________________________________________

9. Using collision theory, explain why reactions between two solutions occur more rapidly than reactions between two solids. (2 marks)

Particles must be able to collide to react.

Only the particles on the surface of a solid are available for reaction.

In a solution, all particles are available. Maximized KE

10. Consider the following reaction: (3 marks)

Mg(s) + 2HBr(aq) → MgBr2(aq) + H2(g) + energy

In terms of collision theory, describe how each of the factors below would influence the reaction rate.

. a) Greater concentration and more collisions. Therefore more successful collisions and

a greater rate.

b) Fewer collisions with sufficient energy to overcome PE barrier. Therefore, a lower

rate.

c) Increased surface area leads to more collisions and more successful collisions.

therefore, a higher rate.

a) Increasing the concentration of HBr :________________________________

________________________________________________________________

b) Decreasing the temperature : _______________________________________

__________________________________________________________________

c) Increasing the surface area of Mg : __________________________________

___________________________________________________________________

11. Consider the following equilibrium:

CS2 (g) + 3Cl2 (g) CCl4 (g) + S2Cl2 (g) H = -238 kJ

a) Sketch a potential energy diagram for the reaction above and label H. (2 marks)

b) Some CS2 is added and equilibrium is then reestablished. State the direction of the equilibrium shift and the resulting change in [Cl2] (1 mark)

b) The temperature is decreased and equilibrium is then reestablished. What will the effect be on the value of Keq ? (1 mark)

12. State Le Chatelier’s Principle. (2 marks)

13. Consider the following graph for the reaction:

energy + N2O4 (g) 2NO2 (g)

a) What is the stress imposed at time t1 ? (1 mark)

b) What is the stress imposed at time t3 ? (1 mark)

c) Calculate Keq for the equilibrium between t2 and t3 . (2 marks)

14. Consider the following equilibrium:

Fe3+ (aq) + SCN- (aq) FeSCN2+ (aq)

Initially, 50.0mL of 0.10M Fe3+ is added to 30.0mL of 0.20M SCN-

At equilibrium, the concentration of FeSCN2+ is found to be 0.050M.

Calculate the Keq for the reaction. (4 marks)

15.Consider the following equilibrium system:2COF2(g) CO2 (g) + CF4 (g) Keq= 2.00

A 2.00 L container is filled with 0.500 mol of COF2. Calculate the [COF2] at equilibrium. (5 marks)

16. Consider the following equilibrium:

CH4(g) + H2O(g) ⇄ CO(g) + 3H2(g)

Keq Temperature

1.78 × 10-3 800℃4.68 × 10-2 1000℃

Is the forward reaction in this equilibrium exothermic or endothermic? Explain your answer. (2 marks)

Keq is increasing therefore products favored, temp increasing and increase in temp favors the endothermic side, therefore forward must be endo

17.A 100.0mL sample of 0.600 M Ca(NO3)2 is diluted by adding 400.0mL of water. Calculate the concentration of ions in the resulting solution. (2 marks)

18. A maximum of 0.60g Pb(NO3)2 can be added to 1.5 L of NaBr(aq)without forming a precipitate. Calculate the [NaBr] (4 marks)

19.

a) Write the balanced formula equation for the reaction between Na3PO4(aq) and CuCl2(aq). (1mark)

b) Write the net ionic equation for the reaction between Na3PO4(aq) and CuCl2 (aq). (1 mark)

20. A saturated solution of nickel carbonate, NiCO3, contains 0.090g in 2.0L of solution. Calculate Ksp for NiCO3. (3 marks)

21. Consider the following Bronsted-Lowry equilibrium:

H2SO3 (aq) + HPO4 -2(aq) H2PO4- (aq) + HSO3

- (aq)

a) Identify the two Bronsted-Lowry acids in the above equilibrium. (1 mark)

22. Consider the salt sodium oxalate, Na2C2O4 .

a) A 1.0M solution of sodium oxalate turns pink when a few drops of the indicator phenolphthalein are added. Write a hydrolysis equation and explain why this salt causes the indicator to change colour. (2 marks)

b) Calculate the equilibrium constant for the hydrolysis above (1 mark)

23. Calculate the pH of 0.50M H3BO3. (4 marks)

24.A 25.0mL sample of Sr(OH)2 is titrated with a standardized solution of HCl to the equivalence point.

a) Write the formula equation for the neutralization. (1 mark)

b) Write the net ionic equation for the neutralization. (1 mark)

c) What is meant by the term “standardized” solution? (1 mark)

d) Define equivalence point.

25. Consider the following amphiprotic anions reacting with each other:

HC6H5O7 -2HC2O4 ?

a) Complete the Brönsted-Lowry acid-base equilibrium for the predominant reaction. (1 mark)

b) Does the equilibrium above favour reactants or products? Explain. (1 mark)

26. A 0.0200M solution of methylamine, CH3NH2, has a pH = 11.40.

Calculate the Kb for methylamine. (4 marks)

27.A titration was performed by adding 0.175M H2C2O4 to a 25.00mL sample of NaOH. The following data was collected: (Note**the average volume that is most unlike the others (outlier) is omitted from calculation)

a) Calculate the [NaOH]. (3 marks)

28. Consider the following equilibrium:

energy + 2H2O H3O+ + OH-

a) Explain how pure water can have a pH = 7.30. (2 marks)

c) Calculate the value of Kw for the sample of water with a pH = 7.30. (2 marks)

29.A) Write the equation for the predominant reaction of HC2O4 - with HSO3

. (1 mark)

HC2O4 - + HSO3 __________ + ___________

B) Identify a Br¿nsted-Lowry conjugate acid base pair from the above reaction. (1 mark)

Acid:__________________________ Base:______________________________

30. A 0.20M solution of a weak acid, HA, has a pH 1.32.

Use calculations and the table of “Relative Strengths of Brønsted-Lowry Acids

and Bases” from the Data Booklet to determine the identity of the acid. (5 marks)

The Acid is:________________________.

31.Balance the following redox reaction in acidic solution:

RuO4 P Ru(OH)2 2H3PO3 (acid) (3 marks)

32.A technician tests the concentration of methanol, CH3OH, in diluted windshield washer fluid using a redox titration. A 25.00mL sample is titrated with 14.50mL of 0.0200M KMnO4. Determine the concentration of methanol in the sample given the following redox reaction:

6H2MnO45CH3OH 5CH2O 2Mn28H2O (3 marks)

33. An electrolytic cell can be used to plate a copper penny with a silver coating. Sketch a diagram of the electrolytic cell. Label the cathode and show the direction of electron flow. (2 marks)

34. What is an electrolytic cell? (2 marks)

35. Consider the following electrochemical cell:

a) Calculate the initial cell voltage. (1 mark)

b) What is the purpose of the salt bridge? (1 mark)

36. Consider the electrolysis of 1.0M H2SO4 using inert platinum electrodes.

a) Write the oxidation half-reaction. (1 mark)

b) Write the reduction half-reaction. (1 mark)

37.Balance the following redox reaction in basic solution. (3 marks)

MnO4C2O4

2MnO2 CO2 (basic)

38. Describe two chemically different methods that can be used to prevent corrosion of iron and explain why each method works.

(2 marks)

Method 1:

Explanation:

Method 2:

Explanation:

39.a) Indicate in the blank spaces on the following chart whether or not a reaction will occur when the metals are added to aqueous ions.

(1 mark)

b) List the oxidizing agents in order of strongest to weakest.

40. Draw and label the parts of an operating electrochemical cell using a zinc anode that will produce an electric current having a voltage of 1.56V at standard conditions. (4 marks)

41. Aluminum is a stronger reducing agent than copper. What is meant by the

term stronger reducing agent?

(2 marks)

42.Consider the following redox reaction in acidic solution:

MnO4- + H2O2 Mn2+ + O2 (Acidic)

a) Write a balanced equation for the above reaction. (4 marks)

b) The above reaction was used for a redox titration. At the equivalence point

5.684 X10-4mol KMnO4 was required to titrate 5.00mL of H2O2 solution.

Calculate the [H2O2]. (2 marks)

43.Sodium metal is produced commercially by the electrolysis of molten NaCl(l).

Explain why sodium metal, Na(s), cannot be produced by electrolysis of

Aqueous NaCl(aq)(2 marks) H2O is more easily reduced than Na+

44. Blister copper is an impure sample of copper containing small amounts of

zinc and gold. Blister copper is purified using electrolysis.

Sufficient voltage is supplied to oxidize copper at the anode.

a) What happens to the zinc at the anode? Explain. (1 mark)

b) Write the equation for the half-reaction that occurs at the cathode. (1 mark)

. a) Zn is oxidized.

It is an even stronger reducing agent than the copper.

b) Cu2+ + 2e- → Cu

45. A sample of copper is placed in HNO3(aq) and another sample of copper is

placed in HCl(aq)

a) In which acid does the copper react? (1 mark)

b) Calculate E° for the reaction that occurs. (1 mark)

. a) Copper reacts in HNO3(aq).

b) E° is + 0.62 volts

46.Using your table, write the half reactions and complete redox reaction when acidified BrO3

- reacts with H2S gas. Label the oxidizing agent and reducing agent. Is this reaction spontaneous? (3 marks)