Chapter 24 Multiple choice questions

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. This question concerns the six-membered ring benzene.
When considering rotation about its centre, which of the following co-linear axes is the same as a rotation about 180°?

${\text{C}}_{\text{6}}^{\text{3}}$ ${\text{C}}_{\text{2}}^{\text{1}}$ correct incorrect

${\text{C}}_{\text{6}}^{\text{2}}$ ${\text{C}}_{\text{6}}^{\text{4}}$ correct incorrect

${\text{C}}_{\text{6}}^{\text{6}}$ correct incorrect

${\text{C}}_{\text{2}}^{\text{2}}$ correct incorrect

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. This question concerns the planar cyclopentadiene anion.
Which of the following statements is NOT correct?

The anion has a C₅ axis or rotation. correct incorrect

The anion has an improper axis of rotation. correct incorrect

The plane of the ion is a reflection plane. correct incorrect

The anion has five mirror planes, each of which passes through a carbon and the centre of the ring. correct incorrect

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. This question concerns the linear molecule ethyne, $\mathrm{H}—\mathrm{C}\equiv \mathrm{C}—\mathrm{H}$.
Which of the following statements is NOT correct?

The principal axis is a C₂ plane. correct incorrect

The molecule has a C₂ symmetry centred about the midpoint of the $\mathrm{C}\equiv \mathrm{C}$ bond. correct incorrect

The molecule has an infinite number of σ_V mirror planes. correct incorrect

The molecule has a centre of symmetry located at the midpoint of the $\mathrm{C}\equiv \mathrm{C}$ bond. correct incorrect

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. This question concerns the square planar molecule xenon tetrafluoride molecule in Worked Example 24.5.
Which of the following statements is NOT correct?

The molecular plane goes through all five atoms. correct incorrect

The molecule has one horizontal reflection plane σ_h. correct incorrect

The molecule has four vertical reflection planes σ_v: two go through the fluorine atoms and two bisect the $\mathrm{F}—\mathrm{Xe}—\mathrm{F}$ bonds. correct incorrect

The molecule has two rotation axes about the central xenon. correct incorrect

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. This question concerns the pyramid ammonia molecule in Worked Example 24.7.
Which of the following statements is NOT correct?

The molecule has three vertical reflection planes σ_v, each of which goes through the central nitrogen and one hydrogen. correct incorrect

The molecule has a three-fold rotation axis about the central nitrogen. correct incorrect

The molecule has a centre of symmetry. correct incorrect

The molecule has no mirror plane perpendicular to the vertical reflection planes σ_v. correct incorrect

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. This question concerns the octahedral molecule tungsten hexacarbonyl in Worked Example 24.8.
Which of the following statements is NOT correct?

The molecule has three two-fold rotation axes about the central tungsten. correct incorrect

The molecule has three four-fold rotation axes about the central tungsten. correct incorrect

The molecule has a centre of symmetry located at the central tungsten. correct incorrect

The molecule has eight three-fold rotation axes, each located in the centre of a $\mathrm{CO}—\mathrm{Co}—\mathrm{Co}$ face of the octahedron. correct incorrect

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. This question concerns the tetrahedral molecule carbon tetrachloride. Its structure appears in Self test 24.2.3.
Which of the following statements is NOT correct?

The molecule has three mirror planes, each defined by a $\mathrm{CL}—\mathrm{C}—\mathrm{Cl}$ plane. correct incorrect

The molecule has four three-fold rotation axes about the central carbon. correct incorrect

The molecule has a centre of symmetry. correct incorrect

The molecule has an improper axis of rotation. correct incorrect

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. This question describes the structure of water H₂O. Its structure appears in Worked Example 24.6.
Which of the following statements is NOT correct?

The molecule has two C₂ reflection axes. correct incorrect

The molecule has two σ_h rotation axes. correct incorrect

The molecule has no centre of symmetry. correct incorrect

The molecular plane is a reflection axis. correct incorrect

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. Which of the following molecules does not have a centre of symmetry?

Boron trichloride, BCl₃ (structure on page 414) correct incorrect

Methane, CH₄ (structure on page 427) correct incorrect

W(CO)₆ (structure on page 420) correct incorrect

Benzene, C₆H₆ (structure on page 424) correct incorrect

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. This question describes the structure of the five-membered ring heterocycle pyrrole. Its structure appears in Self test 24.1.2.
Which of the following statements is NOT correct?

The molecule has no improper axis of rotation. correct incorrect

The molecule has no centre of symmetry. correct incorrect

The molecule has five-fold symmetry about the centre of the five-membered ring. correct incorrect

The molecular plane acts as a reflection axis. correct incorrect