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Chemistry 30

Diploma-style multiple-choice practice with instant checking, plus original written-response questions you can submit for personalized feedback.

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science

Chemistry 30

Diploma-style multiple choice and numerical response practice

Progress0/60
1
Thermochemistry
A reaction releases heat to its surroundings. The reaction is classified as
2
Thermochemistry
In a calorimetry experiment, some heat escapes to the air around the calorimeter. Compared with the accepted value, the experimental molar enthalpy of combustion will be
3
Thermochemistry
Which statement about activation energy is correct?
4
Thermochemistry
Source · Reaction energy profile
Potential energy profile for a reaction The products are at a higher potential energy than the reactants. Reaction progress Potential energy Reactants Products ΔH

This original diagram shows the relative potential energies of the reactants and products.

Based on the potential-energy profile, this reaction
5
Thermochemistry
Hess’s law states that the enthalpy change of a reaction
6
Electrochemistry
In any electrochemical cell, oxidation always occurs
7
Electrochemistry
In the reaction Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s), the oxidizing agent is
8
Electrochemistry
A voltaic cell differs from an electrolytic cell in that a voltaic cell
9
Electrochemistry
The oxidation number of chromium in the dichromate ion, Cr₂O₇²⁻, is
10
Electrochemistry
During the electrolysis of molten sodium chloride, the product formed at the cathode is
11
Electrochemistry
A spontaneous redox reaction has a net cell potential that is
12
Equilibrium & Acid-Base
A closed system reaches chemical equilibrium when
13
Equilibrium & Acid-Base
For the equilibrium N₂O₄(g) + energy ⇌ 2 NO₂(g), increasing the temperature will
14
Equilibrium & Acid-Base
According to the Brønsted–Lowry definition, an acid is a substance that
15
Equilibrium & Acid-Base
A solution has a hydroxide ion concentration of 1.0 × 10⁻³ mol/L at 25 °C. The pH of the solution is
16
Equilibrium & Acid-Base
Hydrochloric acid is a strong acid and acetic (ethanoic) acid is a weak acid. In solutions of equal concentration, hydrochloric acid will have
17
Equilibrium & Acid-Base
In the reaction HCO₃⁻(aq) + H₂O(l) ⇌ H₂CO₃(aq) + OH⁻(aq), the conjugate acid–base pairs are
18
Equilibrium & Acid-Base
The equivalence point of a titration between a strong acid and a weak base occurs at a pH
19
Organic Chemistry
The IUPAC name of the compound CH₃–CH(CH₃)–CH₂–CH₃ is
20
Organic Chemistry
Compounds with the same molecular formula but different structural arrangements are called
21
Organic Chemistry
Ethene reacts with bromine without the need for ultraviolet light, but ethane requires ultraviolet light to react with bromine. This difference occurs because ethene undergoes
22
Organic Chemistry
Many identical propene molecules bond together to form a long chain used in plastics. This reaction is classified as
23
Organic Chemistry
Which compound belongs to the alcohol family?
24
Thermochemistry
When a chemical system absorbs 42 kJ of heat while doing no expansion work, the enthalpy change of the system is
25
Thermochemistry
Doubling every coefficient in a thermochemical equation causes the stated molar enthalpy for that written equation to
26
Thermochemistry
In a coffee-cup calorimeter, the temperature of the solution rises during a reaction. Relative to the reacting chemicals, the solution is the
27
Electrochemistry
In a spontaneous voltaic cell, the electrode at which reduction occurs is the
28
Electrochemistry
During electrolysis of molten sodium chloride, sodium ions move toward the cathode because the cathode
29
Electrochemistry
A stronger oxidizing agent has a greater tendency to
30
Electrochemistry
The main purpose of a salt bridge in a voltaic cell is to
31
Equilibrium & Acid-Base
At equilibrium in a closed system, the forward and reverse reactions
32
Equilibrium & Acid-Base
Adding a catalyst to a system already at equilibrium will
33
Equilibrium & Acid-Base
For an exothermic equilibrium, increasing temperature causes the equilibrium constant to
34
Equilibrium & Acid-Base
A buffer resists a large pH change because it contains significant amounts of
35
Equilibrium & Acid-Base
At 25 °C, a solution with pH 9.30 has a pOH of
36
Equilibrium & Acid-Base
When Q is smaller than K for a reaction, the system will undergo a net change that
37
Equilibrium & Acid-Base
A Brønsted–Lowry base is a species that
38
Organic Chemistry
Oxidation of a primary alcohol under suitable conditions can produce
39
Organic Chemistry
The functional group in an ester contains
40
Organic Chemistry
Compounds with the same molecular formula but different structural arrangements are
41
Organic Chemistry
Hydrogenation of an alkene normally produces
42
Organic Chemistry
The monomer CH₂=CH₂ forms polyethylene through
43
Organic Chemistry
Compared with a straight-chain isomer, a more highly branched alkane generally has a
44
Organic Chemistry
Complete combustion of a hydrocarbon produces
45
Thermochemistry
A burner transfers 25.1 kJ of heat to 300.0 g of water (c = 4.19 J/g·°C) initially at 15.0 °C. Calculate the final temperature of the water, in °C, to one decimal place.
46
Equilibrium & Acid-Base
Calculate the pH of a 0.010 mol/L solution of HCl(aq), a strong acid. Record your answer to two decimal places.
47
Electrochemistry
Using standard reduction potentials E°(Ag⁺/Ag) = +0.80 V and E°(Ni²⁺/Ni) = −0.26 V, calculate the standard cell potential, in volts, of a voltaic cell built from these half-cells. Record your answer to two decimal places.
48
Equilibrium & Acid-Base
In a 4.00 L vessel at equilibrium, there are 2.0 mol of H₂(g), 2.0 mol of I₂(g), and 8.0 mol of HI(g) in the system H₂(g) + I₂(g) ⇌ 2 HI(g). Calculate the value of the equilibrium constant, Kc.
49
Thermochemistry
The molar enthalpy of combustion of propane is −2 219 kJ/mol. Calculate the heat released, in kJ, when 0.250 mol of propane burns completely. Record the magnitude of your answer to the nearest whole number.
50
Organic Chemistry
Determine the number of carbon atoms in one molecule of 3-ethyl-2,4-dimethylhexane.
51
Thermochemistry
A 2.50 g metal sample absorbs 125 J and warms by 20.0 °C. Calculate its specific heat capacity, in J/(g·°C), to two decimal places.
52
Electrochemistry
A current of 1.50 A flows for 1 200 s. Calculate the electric charge transferred, in coulombs.
53
Equilibrium & Acid-Base
Calculate the pOH of a solution whose hydroxide-ion concentration is 2.5 × 10⁻⁴ mol/L. Record the answer to two decimal places.
54
Equilibrium & Acid-Base
A 20.0 mL sample of 0.150 mol/L HCl is neutralized by 0.100 mol/L NaOH. Calculate the required NaOH volume, in mL.
55
Equilibrium & Acid-Base
For A(g) ⇌ B(g), an equilibrium mixture contains [A] = 0.20 mol/L and [B] = 0.80 mol/L. Calculate Kc.
56
Organic Chemistry
Calculate the number of hydrogen atoms in one molecule of the alkane containing 8 carbon atoms.
57
Thermochemistry
A reaction releases 36.0 kJ when 0.150 mol reacts. Calculate the molar enthalpy, in kJ/mol, including its sign.
58
Electrochemistry
Using E°cathode = +0.34 V and E°anode(reduction) = −0.76 V, calculate E°cell, in volts.
59
Equilibrium & Acid-Base
A strong acid solution has pH 3.00. Calculate its hydrogen-ion concentration, in mol/L, using scientific notation.
60
Organic Chemistry
Calculate the molar mass, in g/mol, of propane, C₃H₈, using C = 12.01 and H = 1.01.
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Part two

Written response

biotech

Chemistry 30

Written-response practice and personalized feedback

Progress0/7
1
Thermochemistry12 marks

Comparing Fuels by Calorimetry and Hess’s Law

Alberta Ace Original Practice

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Evaluating a Camp Stove Fuel

A student burns 1.42 g of methanol (CH3OH, M = 32.04 g/mol) in a simple calorimeter that heats 250.0 g of water from 18.6 °C to 44.3 °C. The specific heat capacity of water is 4.19 J/g·°C.

  1. (2 marks) Calculate the heat absorbed by the water. Show your work.
  2. (2 marks) Calculate the experimental molar enthalpy of combustion of methanol. Show your work.
  3. (1 mark) The accepted molar enthalpy of combustion of methanol is −726 kJ/mol. State one reason the experimental value differs from the accepted value.
  4. (2 marks) Write the balanced chemical equation for the complete combustion of methanol, including the enthalpy change as a term in the equation (use the accepted value).
  5. (3 marks) Using standard enthalpies of formation (ΔH°f: CO2(g) = −393.5 kJ/mol; H2O(g) = −241.8 kJ/mol; CH3OH(l) = −239.2 kJ/mol), calculate the molar enthalpy of combustion of methanol producing gaseous water. Show your work.
  6. (2 marks) A camper claims a fuel with a more negative molar enthalpy of combustion is always the better choice. Evaluate this claim, identifying one other factor that should be considered when choosing a fuel.
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2
Electrochemistry12 marks

Designing a Voltaic Cell for a Remote Sensor

Alberta Ace Original Practice

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A Zinc–Silver Power Source

An engineering student builds a voltaic cell using a zinc electrode in 1.0 mol/L Zn(NO3)2(aq) and a silver electrode in 1.0 mol/L AgNO3(aq), connected by a salt bridge containing KNO3(aq).

Standard reduction potentials: Ag+(aq) + e− → Ag(s), E° = +0.80 V; Zn2+(aq) + 2e− → Zn(s), E° = −0.76 V.

  1. (2 marks) Identify the anode and the cathode, and write the half-reaction occurring at each.
  2. (1 mark) Write the balanced net ionic equation for the overall cell reaction.
  3. (1 mark) Calculate the standard cell potential. Show your work.
  4. (2 marks) State the direction of electron flow in the external circuit and the direction of anion movement in the salt bridge.
  5. (2 marks) Predict what happens to the mass of each electrode as the cell operates, and explain why.
  6. (4 marks) The student then recharges a different cell by electrolysis, passing a current of 1.25 A for 45.0 min through a solution of Cu(NO3)2(aq). Calculate the mass of copper deposited at the cathode (M of Cu = 63.55 g/mol; F = 96 500 C/mol). Show your work.
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3
Acids and bases12 marks

Titration of a Household Cleaner

Alberta Ace Original Practice

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Quality Control by Titration

A technician titrates a 10.00 mL sample of an ammonia-based cleaner, NH3(aq), with 0.150 mol/L HCl(aq). The average volume of acid required to reach the equivalence point is 18.40 mL. (Kb of NH3 = 1.8 × 10−5.)

  1. (1 mark) Write the balanced chemical equation for the titration reaction.
  2. (2 marks) Calculate the concentration of ammonia in the cleaner. Show your work.
  3. (2 marks) Identify whether the pH at the equivalence point is less than 7, equal to 7, or greater than 7. Explain your reasoning using the ions present at equivalence.
  4. (2 marks) From the following indicators — methyl orange (colour change pH 3.2–4.4), bromothymol blue (6.0–7.6), phenolphthalein (8.2–10.0) — choose the most appropriate indicator for this titration and justify your choice.
  5. (3 marks) Calculate the pH of a 0.100 mol/L solution of NH3(aq). Show your work.
  6. (2 marks) Sketch or describe the general shape of the titration curve for this weak base–strong acid titration, identifying the approximate starting pH and the direction of the pH change.
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4
Organic chemistry10 marks

Organic Compounds in a Fuel Blend

Alberta Ace Original Practice

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Analyzing Gasoline Additives

A fuel blend contains octane, 2-methylbutane, ethanol, and a small amount of 2-butene. During refining, some hydrocarbons are cracked and others undergo addition reactions.

  1. (2 marks) Draw or write the condensed structural formula for 2-methylbutane and for 2-butene.
  2. (1 mark) Classify 2-butene as saturated or unsaturated, and justify your classification.
  3. (2 marks) 2-Butene reacts with hydrogen gas in the presence of a catalyst. Name the reaction type, and name the product.
  4. (1 mark) Write the IUPAC name of one structural isomer of 2-methylbutane.
  5. (2 marks) Write the balanced chemical equation for the complete combustion of ethanol, C2H5OH(l).
  6. (2 marks) Incomplete combustion of hydrocarbons can occur in a poorly tuned engine. Identify one product of incomplete combustion and one risk it poses to people or the environment.
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5
Chemical equilibrium11 marks

Equilibrium in an Industrial Ammonia Reactor

Alberta Ace Original Practice

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Optimizing Ammonia Production

Ammonia is produced by the exothermic reaction:

N2(g) + 3 H2(g) ⇌ 2 NH3(g) + energy

At equilibrium in a 2.00 L reactor at a set temperature, the vessel contains 0.60 mol N2, 1.20 mol H2, and 0.80 mol NH3.

  1. (1 mark) Write the equilibrium-constant expression (Kc) for this reaction.
  2. (3 marks) Calculate the value of Kc at this temperature. Show your work, including the equilibrium concentrations.
  3. (2 marks) Predict the effect on the equilibrium position of (i) increasing the temperature and (ii) decreasing the volume of the reactor. Justify each prediction.
  4. (1 mark) Explain why an iron catalyst used in this process does not change the value of Kc.
  5. (2 marks) After equilibrium is established, additional H2(g) is injected. Describe how the concentrations of all three gases change as the system re-establishes equilibrium.
  6. (2 marks) Industrial plants run this reaction at a moderately high temperature even though lower temperatures give higher yield. Explain this choice using collision theory or reaction-rate reasoning.
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6
Electrochemistry10 marks

Redox Analysis of a Corroding Culvert

Alberta Ace Original Practice

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Corrosion in the Field

A steel (iron) culvert carrying run-off water shows heavy rusting. A technician proposes attaching blocks of magnesium to the culvert to slow the corrosion. (Standard reduction potentials: Fe2+ + 2e− → Fe, E° = −0.45 V; Mg2+ + 2e− → Mg, E° = −2.37 V; O2 + 2H2O + 4e− → 4OH−, E° = +0.40 V.)

  1. (2 marks) Identify the species oxidized and the species reduced when iron corrodes in oxygenated water, and write the two half-reactions.
  2. (2 marks) Determine the oxidation number of iron in Fe2O3 and in Fe(OH)2.
  3. (2 marks) Explain, using reduction potentials, why magnesium blocks protect the iron culvert.
  4. (1 mark) State the name given to this method of corrosion protection.
  5. (1 mark) Predict what would happen if copper blocks (E° of Cu2+/Cu = +0.34 V) were mistakenly used instead of magnesium.
  6. (2 marks) Balance the following redox equation, which occurs when a technician tests the water with permanganate in acidic solution: MnO4− + Fe2+ + H+ → Mn2+ + Fe3+ + H2O.
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7
Acids and bases10 marks

Buffers and pH in a Mountain Lake

Alberta Ace Original Practice

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Acid Deposition and Natural Buffering

Two lakes receive the same acidic precipitation. Lake A lies on limestone bedrock and its water contains dissolved hydrogen carbonate ions, HCO3−(aq). Lake B lies on granite and has almost no dissolved carbonate species. Over ten years, the pH of Lake A remains near 7.8 while the pH of Lake B falls from 6.9 to 5.4.

  1. (2 marks) Calculate the hydronium ion concentration in Lake B at pH 5.4. Show your work.
  2. (1 mark) Determine how many times more acidic Lake B became as its pH fell from 6.9 to 5.4 (to one significant digit).
  3. (2 marks) Write the equation for the reaction of HCO3−(aq) with hydronium ions, and use it to explain why the pH of Lake A is stable.
  4. (1 mark) Identify the conjugate acid–base pair in your equation from part c.
  5. (2 marks) HCO3− is amphiprotic. Write an equation showing it reacting with a base (OH−), and explain what amphiprotic means.
  6. (2 marks) Predict one biological consequence of the pH change in Lake B, and suggest one human action that could reduce further acidification.
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