Chapter 3 Multiple Choice Questions

. Select the incorrect statement about oxides of cerium.

CeO_1.50_-_1.53 is pyrophoric

CeO_1.74 has the fluorite structure

O₂ is released from CeO₂ by reduction of Ce⁴⁺ to Ce³⁺

The most stable oxide of Ce is Ce₄O₇

. Consider the following statements about lanthanoid sesquioxides Ln₂O₃.
(i) Ln₂O₃ is the most stable oxide for all Ln.
(ii) Lu₂O₃ adopts the A-type hexagonal structure with 7-coordinate Yb³⁺.
(iii) La₂O₃ adopts the A-type hexagonal structure with 7-coordinate La³⁺.
(iv) Lu₂O₃ is more reactive than La₂O₃ with atmospheric CO₂.
(v) Lu₂O₃ is less reactive than La₂O₃ with atmospheric CO₂.
(vi) The magnitude of D_fH° for Eu₂O₃ is much smaller than that for Ce₂O₃.
Now select the correct statement below:

(i), (ii) and (iv) are correct

(iii), (v) and (vi) are correct

(iii), (iv) and (vi) are correct

(i), (iii) and (vi) are correct

. The most stable oxide of Pr is

Pr₁₂O₂₂

Pr₄O₇

Pr₂O₃

PrO₂

. Tetrahalides are known for Ce, Pr and Tb. Select the incorrect statement about Ln tetrahalides from the list below.

PrF₄ may be prepared by oxidation of PrF₃ with F₂.

CeCl₄ may be prepared by oxidation of CeCl₃ with Cl₂.

CeF₄ may be prepared by oxidation of Ce with F₂.

TbF₄ contains 8-coordinate Tb⁴⁺.

. The most important quantity that determines the relative stability of LnCl₃ compared with LnCl₂ is

D_LH°(LnCl₂) - D_LH°(LnCl₃)

D_LH°(LnCl₃) - D_LH°(LnCl₂)

3^rd IP(Ln) - D_atH°(Ln)

1^st IP(Ln) + 2^nd IP(Ln)

. Lanthanoid monoxides LnO all crystallize with the rocksalt structure. The Ln-O distance is 2.516 Å for Ln = Pr, and 2.571 Å for Ln = Eu. The explanation for the difference in Ln-O distance is that

Pr is larger than Eu.

Eu is larger than Pr.

PrO is [Pr³⁺][e^-][O²^-].

EuO is [Eu³⁺][e^-][O²^-].

. Select the incorrect statement about LnI₂ from the list below.

SmI₂ is a useful reducing agent.

TmI₂ is ionic.

EuI₂ is metallic due to the stability of the 4f⁷ configuration.

LaI₂ is [La³⁺][e^-][I^-]₂.

. Consider the following statements about lanthanoid trifluorides LnF₃:
(i) LnF₃ are the least stable Ln trihalides.
(ii) LnF₃ are the most stable Ln trihalides.
(iii) LnF₃ are insoluble in water.
(iv) LnF₃ are soluble in water.
(v) LnF₃ are used in the manufacture of metallic Ln.
(vi) D_?H°(LnF₃) > D_?H°(LnCl₃) (vii) D_?H°(LnF₃) < D_?H°(LnCl₃) Now select the correct statement below:

(i), (iv) and (vii) only are correct

(ii), (iv), (v) and (vi) are correct

(ii), (iii), (v) and (vi) are correct

(i), (iv) and (vi) only are correct

. Consider the following statements about lanthanoid trichlorides LnCl₃:
(i) LnCl₃ are insoluble in water.
(ii) LnCl₃ are soluble in water.
(iii) Ln³⁺ is 8-coordinate in all LnCl₃.
(iv) La³⁺ is 9-coordinate in LaCl₃.
(v) Er³⁺ is 8-coordinate in ErCl₃.
(vi) Er³⁺ is 6-coordinate in ErCl₃.
(vii) CeCl₄ is more stable than CeCl₃.
Now select the correct statement below:

(i), (iii) and (v) only are correct.

(ii), (iv) and (vi) only are correct.

(ii), (iii), (v) and (vii) are correct.

(ii), (iv), (vi) and (vii) are correct.

. Select the incorrect statement about UF₆ from the list below.

UF₆ is an ionic solid

UF₆ is the most thermodynamically stable fluoride of U

UF₆ contains 6-coordinate U

UF₆ melts at 337K

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