Chemistry 30 – Practice Final Exam page 7
Chemistry 30 – Practice Final Exam
Name:______
Unit 1 – Thermochemical Changes
Use the following information to answer the next question
Many insects and small animals have unique defence systems. Bombardier beetles fight off predators with a hot chemical spray. This spray consists of solutions of hydroquinone, C6H4(OH)2(aq), hydrogen peroxide, H2O2(aq), and enzymes which are secreted by the beetles’ glands.
Bombardier Beetle
Reaction Equations Related to Spray Formation
I 2 H2O(l) + O2(g) 2 H2O2(aq) ΔH = +189.2 kJ
II H2O(l) H2(g) + ½ O2(g) ΔH = + 285.8 kJ
III C6H4(OH)2(aq) C6H4O2(aq) + H2(g) ΔH = + 177.0 kJ
A chemical reaction that occurs in order to produce the hot chemical spray can be represented by the equation:
C6H4(OH)2(aq) + H2O2(aq) C6H4O2(aq) + 2 H2O(l)
hydroquinone quinone
1. The heat of reaction for the production of this hot chemical spray is
A -489.2 kJ
B -203.4 kJ
C -82.4 kJ
D +12.2 kJ
Numerical Response1. A student heated a 120.0 g sample of H2O(l) from 21.0°C to 32.5°C by adding
5.93 kJ of energy. The student then used this data to calculate the specific heat capacity of water and compared it with the standard value. The experimental percentage difference was ______%.
(Record your three-digit answer in the numerical response section on the answer sheet.)
Use the following diagram to answer the next question
2. The energy barrier that must be overcome for the forward reaction to occur is called the i , and in the diagram above, it is the difference between ii .
The statement above is completed by the information in row
Row / i / iiA / enthalpy change / I and II
B / enthalpy change / I and III
C / activation energy / I and II
D / activation energy / I and III
3. Which of the following is not true of both endothermic and exothermic reactions?
A Energy is required to break bonds in the reactants.
B Energy is produced as new bonds form in the products.
C The amount of energy absorbed is less than the amount of energy released.
D The energy is stored in chemical bonds as potential energy.
4. When 1.65 g of ethanal, CH3CHO(l) is burned in a calorimeter to produce H2O(l) and CO2(g), 44.7 kJ of heat energy is produced. According to this experimental data, the molar enthalpy of combustion of ethanal is
A +1.52 x 103 kJ/mol
B -76.6 kJ/mol
C -165 kJ/mol
D -1.19 x 103 kJ/mol
Unit 2 – Electrochemical Changes
5. As H2S(g) forms S(s), according to the reaction:
2 H2S(g) + O2(g) 2 H2O(g) + 2 S(s) , the oxidation number of sulfur
A changes from 0 to -2 and sulfur is reduced.
B changes from -2 to 0and sulfur is oxidized.
C decreases by 2 and hydrogen sulfide acts as the reducing agent.
D stays the same because the sulfur is neither oxidized nor reduced.
Use the following information to answer the next question
At one time, an aqueous solution of formaldehyde called formalin, CH2O(aq), was used as a disinfectant and as a tissue preservative. Today, formalin is commonly used in the industrial preparation of plastics and resins.
Formalin can be produced by reacting methanol with acidified potassium dichromate, as represented by the following unbalanced equation.
_ CH3OH(l) + _ Cr2O72-(aq) + _ H+(aq) _ CH2O(aq) + _ Cr3+(aq) + _ H2O(l)
6. When the equation is balanced, it will read as follows:
A CH3OH(l) + Cr2O72-(aq) + 14 H+(aq) CH2O(aq) + 2 Cr3+(aq) + 7 H2O(l)
B 3 CH3OH(l) + Cr2O72-(aq) + 14 H+(aq) 3 CH2O(aq) + 2 Cr3+(aq) + 7 H2O(l)
C 3 CH3OH(l) + Cr2O72-(aq) + 8 H+(aq) 3 CH2O(aq) + 2 Cr3+(aq) + 7 H2O(l)
D 3 CH3OH(l) + Cr2O72-(aq) + 8 H+(aq) 3 CH2O(aq) + 2 Cr3+(aq) + 8 H2O(l)
Use the following information to answer the next question
A student used an acidified 6.31 x 10-2 mol/L KMnO4(aq) solution to titrate 25.0 mL samples of Fe2+(aq) solution of unknown concentration. In the reactions, the Fe2+(aq) ion was oxidized to the Fe3+(aq) ion. The student completed five trials and summarized the data in a table.
trial number / 1 / 2 / 3 / 4 / 5final buret reading (mL) / 17.55 / 35.65 / 26.40 / 42.65 / 16.85
initial buret reading (mL) / 0.30 / 17.55 / 10.05 / 26.40 / 0.55
final colour / purple / purple / pink / pink / pink
7. According to the student’s data, the concentration of Fe2+(aq) is
A 0.206 mol/L
B 0.218 mol/L
C 0.213 mol/L
D 0.223 mol/L
8. The half-reaction to which all other half-cell potentials are compared is
A Li+(aq) + e– Li(s)
B Au3+(aq) + 3 e– Au(s)
C F2(g) + 2 e– 2 F–(aq)
D 2 H+(aq) + 2 e– H2(g)
Use the following information to answer the next question
Hydrogen-oxygen fuel cells have been used for years in spacecraft and more recently in small-scale power plants to generate electricity. Now, some governments and companies are working together to perfect this type of fuel cell for automobile use, and experiments are being conducted with operational prototypes. A diagram of a hydrogen-oxygen fuel cell is shown below.
Numerical Response2. In the diagram above, the anode, the cathode, the electrolyte, and a product of the reaction are labeled, respectively, _____, _____, _____, and _____.
(Record your four-digit answer in the numerical-response section on the answer sheet.)
Use the following information to answer the next two questions
Copper can be refined (purified) using an apparatus like the one shown below, which is a small-scale version of an industrial apparatus.
9. In this electrochemical cell, the purified copper sheet acts as the
A anode and is the site where SO42-(aq) ions are oxidized
B cathode and is the site where SO42-(aq) ions are reduced
C anode and is the site where Cu2+(aq) ions are oxidized
D cathode and is the site where Cu2+(aq) ions are reduced
Numerical Response3. If the direct current power supply produces a steady 3.50 A current, then the time required to deposit 0.100 g of purified copper is _____ s.
(Record your three-digit answer in the numerical response section on the answer sheet.)
Unit 3 – Chemical Changes of Organic Compounds
Use the following information to answer the next question
A student added a bromine solution to a hydrocarbon sample that contains an isomer of C7H14(l) in the absence of light. After shaking the sample, the student observed that the colour of the bromine solution changed from orange to colourless.
10. An interpretation that could be made from the student’s observation is that the hydrocarbon sample is i , and the IUPAC name of the sample could be ii .
The statement above is completed by the information in row
Row / i / iiA / saturated / hept-2-ene
B / saturated / cyclohexane
C / unsaturated / hept-2-ene
D / unsaturated / cyclohexane
11. Which of the following is not a structural isomer of C7H14?
A cyclo-octane
B 2-methylhex-3-ene
C 2,2-dimethylpent-2-ene
D trimethylbut-1-ene
12. When propan-1-ol and methanoic acid react, in the presence of an acid catalyst, the products are
A methyl propanoate only
B propyl methanoate only
C methyl propanoate and water
D propyl methanoate and water
Use the following information to answer the next question
There are several methods of producing chloroethane, which can be used as a solvent and a refrigerant.
Reactants / Type of Reaction1 ethene / 5 condensation
2 ethane / 6 addition
3 ethyne / 7 elimination
4 ethanol / 8 substitution
Numerical Response
4. Match the reactants and type of reaction numbered above with the two methods of producing chloroethane below. (2 marks)
Method I
______+ Cl-Cl H – C – C – Cl + HCl which is a(n) ______reaction.
Reactant Product
(Record in (Record in
1st column) 2nd column)
Method II
______+ H – Cl H – C – C – Cl which is a(n) ______reaction.
Reactant Product
(Record in (Record in
3rd column) 4th column)
Use the following information to answer the next question
5. Match the IUPAC name or the organic term numbered above with its descriptor below: (2 marks)
Product name ______(Record in first column)
Reactant name ______(Record in second column)
Type of organic reaction ______(Record in third column)
Classification of product ______(Record in fourth column)
Unit 4 – Chemical Equilibrium Focussing on Acid-Base Systems
13. Sour pickles have pH of about 3.00. The [OH-] in a typical sour pickle is
A 1.0 x 10-11 mol/L
B 3.0 x 10-11 mol/L
C 1.0 x 10-3 mol/L
D 3.0 x 10-3 mol/L
Use the following information to answer the next three questions
Coal and natural gas contain trace amounts of sulphur compounds, which when burned, may lead to acid rain pollution.
Reactions Related to Acid Rain
I 2 H2S(g) + 3 O2(g) 2 H2O(g) + 2 SO2(g)
II 2 SO2(g) + O2(g) 2 SO3(g)
III SO2(g) + H2O(l) H2SO3(aq)
IV SO3(g) + H2O(l) H2SO4(aq)
14. The equilibrium law expression for reaction I is
A
B
C
D
15. The conjugate base of H2SO3(aq) is
A HSO3 –(aq)
B SO32 –(aq)
C OH–(aq)
D H2O(l)
Use the following additional information to answer the next question
At 900 K, the equilibrium constant for reaction II is 13.0. The equilibrium concentrations are [SO2] = 0.361 mol/L and [SO3] = 0.840 mol/L
16. Given the values above, the calculated equilibrium concentration of O2(g) is
A 0.179 mol/L
B 0.416 mol/L
C 2.40 mol/L
D 5.59 mol/L
17. Which of the following mixtures could act as buffer solutions?
A HF(aq) and H2S(aq)
B NaOH(aq) and HCl(aq)
C Na2CO3(aq) and NH3(aq)
D NaH2PO4(aq) and Na2HPO4(aq)
Use the following information to answer the next question
HNO2(aq) + HCO3 –(aq) NO2–(aq) + H2CO3(aq)
18. In the reaction represented by the equation above, an amphiprotic species is i , and a conjugate acid-base pair is ii .
The statement above is completed by the information in row
Row / i / iiA / HNO2(aq) / HNO2(aq) and H2CO3(aq)
B / HNO2(aq) / H2CO3(aq) and NO2–(aq)
C / HCO3 –(aq) / H2CO3(aq) and HCO3 –(aq)
D / HCO3 –(aq) / HCO3 –(aq) and NO2–(aq)
Use the following information to answer the next question
A student titrated an unknown sample an aqueous acid with an unnamed base. The data are graphed below:
19. The graph of the student’s titration data shows the titration of i acid with a strong base, and on the graph the equivalence point is indicated by point ii .
The statement above is completed by the information in row
Row / i / iiA / weak / II
B / strong / II
C / strong / III
D / weak / III
Written Response
2 questions: #1. analytical question
#2 holistic question
Written Response – Question 1 (analytical)
Use the following information to answer this question
Fireball Horror of Aerosol Can Blast
A housewife was engulfed in a fireball when she tried to separate two cans of hairspray that were taped together. She accidentally punctured one aerosol can with a knife as she cut the tape.
A jet of butane gas shot into her living room fireplace, ignited, then immediately exploded into a fireball that destroyed the room and enveloped the housewife in flames.
Melting point of butane -138.0°C
Boiling point of butane -1.0°C
Hairspray use of butane solvent and propellant
1. a) Draw a structural diagram for butane (condensed or line structural diagram)
b) Write the balanced chemical equation for the combustion reaction that occurred and calculate the molar enthalpy of combustion for butane.
c) Instead of butane, non-flammable substances such as chlorofluorocarbons
(e.g. CF2Cl2) are sometimes used as solvents and propellants for aerosol products. Select a position either for or against the continued use of butane as a propellant for aerosol cans. State one reason (not already given) to back up your answer.
Written Response – Question 2
2. The Haber-Bosch process for the industrial production of ammonia involves the equilibrium
N2(g) + 3 H2(g) 2 NH3(g) + 92.2 kJ
In a laboratory experiment designed to study this equilibrium, a chemical engineer injects 0.20 mol of N2(g) and 0.60 mol of H2(g) into a 1.0 L flask at 500°C. She records her analysis of the contents of the flask at 5 s intervals in the table shown.
Time (s) / Concentration (mol/L)N2(g) / H2(g) / NH3(g)
0 / 0.20 / 0.60 / 0.00
5 / 0.14 / 0.42 / 0.12
10 / 0.11 / 0.33 / 0.18
15 / 0.10 / 0.30 / 0.20
20 / 0.10 / 0.30 / 0.20
25 / 0.10 / 0.30 / 0.20
Analyze the data. Your response should include:
• a plot of the concentrations of N2(g), H2(g), and NH3(g) versus time on the grid provided below, including appropriate title
• the time required to reach equilibrium
• the equilibrium constant for the reaction
• two methods, other than increasing reactant concentrations, that could increase the yield of ammonia
Written Response – Question 2 continued