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05 Alkanes and Radical Reactions Online Quiz Questions

Use this free practice quiz with 20 questions to review 05 Alkanes and Radical Reactions, test your knowledge, and prepare for your next test or exam.

20 questions
01
True or false
1 point

An acyclic alkane containing four carbon atoms has the molecular formula C4H10\mathrm{C_4H_{10}}.

  1. A

    True

  2. B

    False

02
Choose one
1 point

In a Newman projection viewed along a carbon–carbon bond, which symbol represents the rear carbon?

  1. A

    A dot

  2. B

    A circle

  3. C

    A wedge

  4. D

    A dashed line

03
True or false
1 point

When an alkane rotates around a carbon–carbon single bond, its conformation can change without changing which atoms are connected.

  1. A

    True

  2. B

    False

04
Written response
1 point

In ethane, what is the conformation called when the front and rear C–H bonds are offset rather than lined up?

05
Fill in the blank
1 point

The energy required to break a bond homolytically into two radicals in the gas phase is called .

06
Choose one
1 point

When viewing butane along its central carbon–carbon bond, which staggered conformer is lower in energy, and how far apart are its methyl groups?

  1. A

    Gauche, because the methyl groups are 180° apart

  2. B

    Gauche, because the methyl groups are 60° apart

  3. C

    Anti, because the methyl groups are 180° apart

  4. D

    Anti, because the methyl groups are 60° apart

07
True or false
1 point

A reaction with a favorable overall energy change is not necessarily fast, because its activation-energy barrier may still be large.

  1. A

    True

  2. B

    False

08
Fill in the blank
1 point

In the initiation step of radical halogenation, homolytic cleavage of X2\mathrm{X_2} produces .

09
Choose one
1 point

Two possible hydrogen-substitution sites would form a primary alkyl radical or a tertiary alkyl radical. Based on the general radical-stability trend, which radical is more stable?

  1. A

    The primary alkyl radical

  2. B

    They are always equally stable

  3. C

    The tertiary alkyl radical

  4. D

    The radical with the more available hydrogens

10
Choose all
1 point

Which reactions are propagation steps in a radical halogenation chain? Select all correct choices.

  1. A

    X⋅+R−H→H−X+R⋅\mathrm{X\cdot + R-H \rightarrow H-X + R\cdot}

  2. B

    R⋅+X2→R−X+X⋅\mathrm{R\cdot + X_2 \rightarrow R-X + X\cdot}

  3. C

    X2→2X⋅\mathrm{X_2 \rightarrow 2X\cdot}

  4. D

    R⋅+X⋅→R−X\mathrm{R\cdot + X\cdot \rightarrow R-X}

11
Written response
1 point

A hydrogen-abstraction step breaks a C–H bond with BDE 410 kJ/mol410\ \mathrm{kJ/mol} and forms an H–Cl bond with BDE 430 kJ/mol430\ \mathrm{kJ/mol}. Using ΔH≈∑D(bonds broken)−∑D(bonds formed)\Delta H \approx \sum D(\text{bonds broken})-\sum D(\text{bonds formed}), what is the estimated ΔH\Delta H in kJ/mol?

12
Choose all
1 point

When estimating the mixture of products from radical halogenation, which factors should be considered? Select all correct choices.

  1. A

    How many equivalent hydrogens are available at each possible substitution site

  2. B

    The relative stability of the radicals formed

  3. C

    Only which possible radical is most stable

  4. D

    The halogen used and the reaction conditions

13
Open ended
1 point

Explain how the overall energy change and activation energy differ on a reaction energy diagram. What does activation energy suggest about reaction rate, and why does a favorable overall energy change alone not guarantee a fast reaction?

14
Choose one
1 point

A step in a radical chain combines two radicals to form a molecule and removes both radicals from the chain. What kind of step is this?

  1. A

    Initiation

  2. B

    Termination

  3. C

    Propagation

  4. D

    Hydrogen abstraction

15
Choose one
1 point

An acyclic alkane has seven carbon atoms. Which molecular formula follows from the general formula for acyclic alkanes?

  1. A

    C7H14C_7H_{14}

  2. B

    C7H16C_7H_{16}

  3. C

    C7H12C_7H_{12}

  4. D

    C7H18C_7H_{18}

16
Choose one
1 point

In a Newman projection viewed directly along a carbon–carbon bond, how are the front and rear carbons represented?

  1. A

    The front carbon is a circle, and the rear carbon is a dot.

  2. B

    Both carbons are shown as dots, with the bond drawn between them.

  3. C

    The front carbon is a dot, and the rear carbon is a circle.

  4. D

    The front carbon is omitted, and only the rear carbon is shown.

17
Choose one
1 point

What happens to an alkane molecule when it rotates around a carbon–carbon single bond?

  1. A

    It changes the molecule's three-dimensional arrangement but not which atoms are connected.

  2. B

    It breaks the carbon–carbon bond and changes which atoms are connected.

  3. C

    It changes the number of bonds each carbon has.

  4. D

    It converts the carbon–carbon single bond into a double bond.

18
Written response
1 point

What is the term for a species that contains an unpaired electron?

19
Choose one
1 point

For ethane, which statement correctly compares the staggered and eclipsed conformations?

  1. A

    The eclipsed conformation is lower in energy, and their energy difference is steric strain.

  2. B

    The staggered conformation is lower in energy, and their energy difference is torsional strain.

  3. C

    The staggered conformation is lower in energy, and their energy difference is bond dissociation energy.

  4. D

    The two conformations have the same energy because rotation does not change connectivity.

20
Written response
1 point

What is the full term for the energy required to break a bond homolytically into two radicals in the gas phase?