June 2005

1. What does X represent in the diagram below?

(A) activation energy for the forward reaction

(B) activation energy for the reverse reaction

(C) heat of reaction for the forward reaction

(D) heat of reaction for the reverse reaction

2. Which increases the reaction rate?

(A) decreasing the frequency of collisions

(B) decreasing ªH for the reaction

(C) increasing the frequency of collisions

(D) increasing ªH for the reaction

3. Which observation best supports the Kinetic Molecular Theory?

(A) Acetic acid odour is detected from across the room.

(B) Liquid water freezes at 0°C under standard conditions.

(C) Nitrogen dioxide gas is dark brown in colour.

(D) When burned, butane produces more heat per mole than propane.

4. What is the high energy, unstable chemical species that exists in the transition from

reactants to products?

(A) activated complex

(B) catalyst

(C) inhibitor

(D) reaction intermediate

5. What is the value of ªH for the forward reaction if its activation energy is 20.0 kJ and the

activation energy of the reverse reaction is 30.0 kJ?

(A) -50.0 kJ

(B) -10.0 kJ

(C) 10.0 kJ

(D) 50.0 kJ

6. What affect would increasing the surface area of a solid reactant have on a system

approaching equilibrium?

(A) decreases the rate of the forward reaction

(B) decreases the time to reach equilibrium

(C) increases the equilibrium concentration of products

(D) increases the equilibrium concentration of reactants

7. For the reaction mechanism below, increasing the concentration of which species would

have the greatest effect on the overall reaction rate?

X + Y 6 2 Z slow

Z + 2 W 6 U fast

Z + U 6 V fast

(A) U

(B) V

(C) Y

(D) Z

8. The table below describes two different reactions in which Reaction 1 is faster. What

accounts for this observation?

Reaction 1 Reaction 2

(aq) 4 (aq) (aq) 2 2 4 (aq) Reactants Fe + MnO MnO4 + H C O 2+ - -

Temperature 20 C 40 Co o

Concentration 0.5 mol/L solutions 1.0 mol/L solutions

(A) nature of reactants

(B) solution concentration

(C) surface area

(D) temperature

ªHReaction Mechanism

9. The equilibrium system below is in a test tube at room temperature. When five drops of

3Fe(NO )(aq) is added, a precipitate forms.

4 (aq) 2 7 (aq) (aq)H (aq) + 2 CrO º Cr O + OH + 2- 2- -

yellow orange

2 210. What happens to [O (g)] and [H O(g)] in the equilibrium below if the system is heated?

(aq) 2(g) 2 (g) 2(g) 4 HCl + O º 2 H O + 2 Cl ªH = +113 kJ

211. Given the equilibrium concentrations; [CO(g)] = 0.105 mol/L, [H (g)] = 0.250 mol/L, and

3 eq[CH OH(g)] = 0.00261 mol/L, what is the value of K for the equilibrium below?

(g) 2 3 (g)CO + 2 H º CH OH

(A) 0.0994

(B) 0.398

(C) 2.51

(D) 10.0

12. What happens to the equilibrium below when NO(g) is added to the system?

(g) 2(g) (g) 2 NO + Cl º 2 NOCl

4% 51.(a) Use the table below to answer the following questions.

2 2 Fe + H O ÷ FeOH + HO - 286.1 kJ3+ 3+

2 2 2 2HO + H O 6 H O + HO + 270.4 kJ

2 2 2FeOH + HO 6 Fe + H O + O - 556.7 kJ3+ 3+

i.) Write the equation for the overall net reaction. Identify reaction

intermediate(s) and/or catalyst(s) present.

Reaction Intermediate(s):

Catalyst(s):

2% (b) The system below is at equilibrium.

2 (g) (g) 2(g)H CO º CO + H ªH = 5.36 kJ

eq What effect would increasing the temperature have on the value of K for this

reaction? Justify your answer.

4% (c) Mixtures of hydrogen gas and carbon monoxide are placed in two separate flasks.One

flask is at 1000.0 C and the other is at 1200.0 C. The graph below shows theo o

change in methane concentration over time for each flask.

2(g) (g) 4(g) 2 (g) 3 H + CO º CH + H O ªH = -206 kJ

(i) Mark an “X” on each line in the graph, where equilibrium is first

established.

(ii) Which temperature condition, 1000.0 C or 1200.0 C, iso o

represented by line A in the graph? Provide two reasons for your

answer.

3% (d) The equilibrium below occurs when nitrogen monoxide is placed in a

closed container and decomposes.

(g) 2(g) 2(g)2 NO º N + O

When 0.250 mol of NO(g) is placed in a sealed 1.0 L container at a particular

temperature, 40.0% of it decomposes. Calculate the equilibrium constant at this

temperature.

June 2006

1. According to collision theory, which is true about reactants when a chemical reaction occurs?

(A) They acquire the activation energy.

(B) They are gases.

(C) They are heated.

(D) They have more PE than products.

2. Which letter below represents the heat of reaction?

(A) A

(B) B

(C) C

(D) D

3. Which best indicates the energy as reactants collide and form an activated complex?

4. Which factor explains why coal dust is explosive?

(A) concentration

(B) pressure

(C) surface area

(D) temperature

5. Which reaction occurs fastest at room temperature?

2 2 2(A) 2 H (g) + O (g) 6 2 H O(A)

4 2 4(B) 2 Ag (aq) + CrO 2)(aq) 6 Ag CrO (s) +

2 2(C) Pb(s) + 2 HCl(aq) 6 PbCl (s) + H (g)

4 2 2 2(D) CH (g) + 2 O (g) 6 CO (g) + 2 H O(g)

6. Which is the catalyst in the reaction mechanism below?

2 2 3Step 1: NO (g) + SO (g) 6 SO (g) + NO(g)

2 2Step 2: NO(g) + ½O (g) 6 NO (g)

(A) NO(g)

2(B) NO (g)

2(C) O (g)

2(D) SO (g)

7. How many elementary steps are in the mechanism illustrated below?

(A) 1

(B) 2

(C) 3

(D) 4

8. Which are necessary to establish a dynamic equilibrium?

(A) a changing concentration and a closed system

(B) a constant temperature and an open system

(C) an irreversible reaction and an open system

(D) a reversible reaction and a closed system

(E)

9. The equilibrium below is established in a rigid 1.0 L container.

4 2 2 2CH (g) + 2H S(g) + heat º CS (g) + 4H (g)

4 2If some CH (g) is added to the system, what happens to the concentration of CS (g) and the

value of K?

210. If [F ] = 1.0 × 10 mol/L and [F] = 3.0 × 10 mol/L in the equilibrium below, what is the2 4

value of the equilibrium constant?

2F (g) º 2 F(g)

(A) 9.0 × 10G6

(B) 6.0 × 10G2

(C) 3.0 × 10G2

(D) 1.1 × 105

11. Which is the equilibrium expression for the system below?

3 2 2 2CaCO (s) + 2 HF(g) CaF (s) + H O(g) + CO (g)

12. Which K value indicates a reaction in which products are most favoured?

(A) 1.0 × 102

(B) 1.0 × 10-1

(C) 1.0 × 10 1

(D) 1.0 × 10 2

3% 51. (a) Explain two ways that the rate of CO2(g) production can be increased in the

reaction below.

3(s) (aq) 2(aq) 2(g) 2 (l)CaCO + 2 HCl 6 CaCl + CO + H O

2% (b) What is the equation for step 3 in the reaction mechanism below? Show

workings.

2 2Step 1: 2 NO 6 N O

2 2 2 2 2Step 2: N O + H 6 N O + H O

Step 3: ?

Overall reaction: 2 NO + 2 H2 ÿ N2 + 2 H2O

Step 3: _______________________________________

2% (c) At 1000 K, sulfur dioxide is converted into sulfur trioxide, as shown below.

2 2 3(g) 2 SO (g) + O (g) º 2 SO K = 284

2 2 3If [SO ] = 0.0150 mol/L, [O ] = 0.0250 mol/L, and [SO ] = 0.0400 mol/L, is

the mixture at equilibrium? Justify your answer.

4% (d) The equilibrium below was established under constant temperature

conditions.

2 (aq) 4 (aq) 2Co(H O) + 4 Cl-(aq) º CoCl + 6H O(l) 2+ 2-

pale pink deep blue

3 (i) Explain what color change would occur if AgNO was added to the

system, producing a precipitate.

(ii) When the equilibrium is placed in an ice bath it turns pale pink. Is ªH

for the forward reaction positive or negative? Justify your answer.

2% (e) Explain what happens to the value of K in the equilibrium below when the

temperature of the system is increased.

2 2 3N (g) + 3 H (g) 2 NHR (g) + heat

June 2007

1. In the potential energy diagram below, which represents the activation energy for the

reverse reaction?

(A) A

(B) B

(C) C

(D) D

2. Which is true about an activated complex?

3. When studying the effect of temperature on the rate of the reaction below, what must be

kept constant?

HCl(aq) + NaHCO3(s) 6NaCl(aq) + H2O(l) + CO2(g)

(A) concentration of HCl(aq)

(B) concentration of NaCl(aq)

(C) pressure of reaction vessel

(D) volume of reaction vessel

4. What is produced in one step of a reaction mechanism and consumed in a later step?

(A) activated complex

(B) catalyst

(C) inhibitor

(D) intermediate

5. Which must occur for a chemical reaction to take place?

(A) addition of a catalyst

(B) addition of energy

(C) collisions between reacting particles

(D) formation of a reaction intermediate

6. In the graph below, what is the rate determining step?

(A) A

(B) B

(C) C

(D) D

7. What is true for the equilibrium below?

(aq) (aq) 4 (aq) (l)Co(H2O)6 + 4 Cl- + energy º CoCl + 6 H2O2+ 2-

Pink Blue

(A) Cooling the reaction flask will make the colour turn blue.

(B) Cooling the reaction flask will make the colour turn pink.

(C) Decreasing pressure will make the colour turn blue.

(D) Decreasing pressure will make the colour turn pink.

8. At equilibrium, 2.2 mol of CH4(g), 2.2 mol of H2O(..), 0.12 mol of CO(g) and 0.36 mol of

H2(g) are present in a 1.0 L container. What is the value of Keq for the equilibrium below?

4(g) 2 (l) (g) 2(g)CH + H O º CO + 3 H

(A) 1.2 × 10-3

(B) 2.5 × 10-3

(C) 3.9 × 102

(D) 8.6 × 102

9. The graph below refers to an equilibrium. When does the system reach equilibrium?

(A) A

(B) B

(C) C

(D) D

10. Why is a chemical equilibrium described as dynamic?

(A) Concentration of chemical species remains constant.

(B) Minimum energy is achieved.

(C) Reactants and products continue to form.

(D) Temperature remains constant.

11. In the equilibrium system below, which change would decrease the concentration of O2(g)?

(g) (g) (g)N2 + 2 O2 + energy º N2O4

(A) decrease the concentration of N2(g)

(B) decrease the pressure of the reaction vessel

(C) increase the temperature

(D) increase the volume of the reaction vessel

12. In a 1.0 L container, 2.0 moles of CS2(g) and 4.0 moles of Cl2(g) are mixed to establish the

equilibrium below. If 0.30 moles of CCl4(g) are present at equilibrium, how much Cl2(g)

remains?

(g) (g) (g) (g)CS2 + 3 Cl2 S2Cl2 + CCl4

(A) 0.30 mol

(B) 0.90 mol

(C) 3.1 mol

(D) 3.9 mol

6% 51. (a) Use the table below to answer the following questions.

(i) What is the enthalpy for the overall reaction?

(ii) Identify the reaction intermediate(s) and/or catalyst(s) present.

(iii) Sketch a clearly labelled potential energy diagram for this reaction

mechanism.

3% (b) All Canadian automobiles are equipped with catalytic convertors to improve

air quality.

(i) Using the mechanism below for ozone production, describe how

catalytic convertors decrease ground level ozone concentrations.

(ii) Describe one way to improve the design of a catalytic convertor that

will increase its ability to reduce air pollution.

4% (c) The system below is at equilibrium.

(i) If the gases are in a sealed container, explain the effect increasing the

volume would have on the equilibrium position.

(ii) Explain what effect increasing the temperature of the reaction vessel

would have on the value of Keq for this reaction.

June 2008

1. In the potential energy diagram below, which represents the activation energy for the

catalysed reaction?

(A) A

(B) B

(C) C

(D) D

a a2. In a reaction E (forward) is 28 kJ and E (reverse) is 54 kJ. Which describes the forward

reaction?

3. Marble chips and chalk dust are different forms of CaCO3(s). Which explains the difference

in the reaction rate of each with vinegar?

(A) concentration

(B) pressure

(C) surface area

(D) temperature

4. Which refers to each single step in a reaction mechanism?

(A) activated complex

(B) elementary

(C) intermediate

(D) rate determining

5. Which substance, when added to the reaction mechanism below, will have the greatest

effect on the overall reaction rate?

(A) HOI

(B) H2O

(C) IG

(D) OclG

6. Which predicts how an equilibrium responds to imposed changes?

(A) Arrhenius definition

(B) Faraday’s law

(C) Hess’ law

(D) Le Châtelier’s principle

7. Which change in the equilibrium below will result in the highest concentration of NO(g)?

(A) adding a catalyst

(B) increasing pressure

(C) increasing temperature

(D) removing oxygen

8. The reaction below is allowed to reach equilibrium. If O2(g) is added to the system, what is

the effect on the value of [CO2(g)] and the value of K?

9. When the reaction below is at equilibrium, [Cl2] = 4.4 × 10 mol/L, [N2] = 1.4 × 10-4 -3

mol/L, and [NCl3] = 1.9 × 10 mol/L. What is the value of K?-1

(A) 3.3 × 10-12

(B) 3.2 × 10-6

(C) 3.1 × 105

(D) 3.0 × 1011

10. What is the equilibrium expression for the reaction below?

11. For the equilibrium below, the concentration of CO(g) and Cl2(g) are both 0.200 mol/L.

What is the equilibrium concentration of COCl2?

(A) 0.24

(B) 0.84

(C) 1.2

(D) 4.2

12. A sample of ammonia is placed in a sealed vessel and allowed to reach equilibrium. Using

the graph below, what is the value of K?

(A) 0.029

(B) 0.30

(C) 3.4

(D) 34

51. (a) In a lab, data from two trials of the reaction below were collected. The graph

illustrates the volume of oxygen produced over time for each trial.

i) Which trial has the highest rate of O2 production?

ii) On the diagram below, show how the graph for trial 2 will change if a catalyst

is added after 6 seconds.

iii) Give one factor, other than a catalyst, that could cause the different rates

observed in the graph in part i), and explain how this factor affects the

reaction rate.

51. (b) The mechanism below shows the decomposition of ozone in the upper atmosphere.

i) What is the equation for the overall reaction?

ii) Identify reaction intermediate(s) and/or catalyst(s) present.

Reaction Intermediate(s):

Catalyst(s):

iii) Step 1 of the reaction mechanism does not occur unless ultraviolet radiationis

present. Describe the role that ultraviolet radiation plays in the reaction.

2 251. (c) 0.500 mol of H O (g) are placed in a 2.00 L flask at a certain temperature and

2allowed to establish the equilibrium below. If there are 0.150 mol of O (g) in the

flask at equilibrium, what is K for the reaction?

June 2009

1. Why does decreasing the concentration of a reactant usually decrease the rate of reaction?

(A) causes more intense collisions

(B) decreases the number of collisions per second

(C) lowers the activation energy

(D) provides an alternate reaction mechanism

2. Which graph represents the fastest exothermic reaction?

(A)

(B)

(C)

(D)

3. A student placed 3.0 g of Mg(s) into some HCl(aq) in two different experiments giving the

reaction below. It took more time for all of the Mg(s) to react in the second experiment.

Which accounts for the slower rate in the second experiment?

2 2Mg(s) + 2 HCl(aq) MgCl (aq) + H (g)

(A) a catalyst was added

2(B) [H ] was decreased

(C) Mg was crushed into a powder

(D) temperature was decreased

4. How does adding a catalyst to a reaction affect the reaction pathway and the activation

energy?

Reaction

Pathway

Provided

Activation Energy

(A) alternate higher

(B) alternate lower

(C) same higher

(D) same lower

5. Which step of a reaction is the rate determining step?

(A) fastest

(B) first

(C) last

(D) slowest

26. What is the role of O (g) in the mechanism below?

3 2 2 2Step 1: O (g) + Br (g) ÷ Br O(g) + O (g)

2 2Step 2: Br (g) + O (g) ÷ 2 BrO(g)

2 2Step 3: 2 BrO(g) ÷ Br O (g)

(A) catalyst

(B) intermediate

(C) product

(D) reactant

7. The diagram below illustrates the reverse reaction rate for the equilibrium shown. Which

1explains what happens at t ?

2 2 3 N (g) + 3 H (g) º 2 NH (g) + energy

3(A) [NH ] decreased

3(B) [NH ] increased

(C) pressure is increased

(D) temperature is decreased

8. Which is necessary for equilibrium to occur?

(A) closed system

(B) open system

(C) rate of the forward reaction is zero

(D) rate of the reverse reaction is zero

3 39. Some Fe(NO ) (aq) and NaSCN(aq) are added to a sealed flask and allowed to reach

equilibrium. What happens to the reverse reaction rate and [Fe ] as equilibrium is being3+

reestablished?

Fe (aq) + SCNG(aq) W FeSCN (aq) 3+ 2+

Reverse Rate [Fe ]3+

(A) decreased decreased

(B) decreased increased

(C) increased decreased

(D) increased increased

10. Which describes the temperature and pressure needed for the maximum yield of styrene?

6 5 2 3 6 5 2 2C H CH CH (g) + 123 kJ W C H CHCH (g) + H (g)

styrene

Temperature Pressure

(A) high high

(B) high low

(C) low high

(D) low low

11. Which chemical equation corresponds to the equilibrium constant expression shown below?

(A) 2A + 3B W C

(B) A + B W C

(C) C W A + B

(D) C W 2A + 3B

4 2 eq12. At equilibrium, [CCl ] = 0.28 mol/L and [Cl ] = 0.060 mol/L. What is the value of K ?

4 2CCl (g) W C(s) + 2 Cl (g)

(A) 3.9 × 10!4

(B) 1.3 × 10!2

(C) 2.1 × 10!1

(D) 7.8 × 101

51.(a) The reaction below has an activation energy of 209 kJ. Sketch a potential energy diagram

for the reaction, and label the activation energy and heat of reaction.

2 2 32 NO (g) + O (g) + 199 kJ 2 NO (g)

2(b) For the reaction below, it takes longer to collect 35 mL of CO (g) using acid at room

temperature compared to acid at 60.0 EC. Explain why.

3 2 4 2 4 2CaCO (s) + H SO (aq) CO (g) + CaSO (s) + H O(l)

(c) Using collision theory, explain why zinc metal reacts more rapidly in concentrated

HCl(aq) than in dilute Hcl(aq).

(d) Inside a propane tank, the equilibrium below is created. When propane gas is

released from the tank, explain why condensation forms on the outside of the tank.

3 8 3 8 C H (l) + Energy º C H (g)

2 2(e) For the reaction below, the graph shows how A (g) and B (g) come to equilibrium

with AB(g) at constant temperature in a 1.0 L flask. Calculate the equilibrium

constant.

2 2A (g) + B (g) º 2 AB(g)

eq 2 4(f) Calculate K if 1.0 mol of N O is initially placed into a 1.0 L vessel, and at

2 4equilibrium 0.75 mol of N O remains in the vessel.

2 4 2N O (g) º 2 NO (g)