Unit 11: d- and f-Block Elements — Online MCQ Test
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Practice Unit 11: d- and f-Block Elements with a free chapter-wise online MCQ test.
This chapter covers: Transition Elements General introduction electronic configuration occurrence and characteristics general trends in properties of the first-row transition elements - physical proper....
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Unit 11: d- and f-Block Elements — Important Questions & Answers
The calculated spin only magnetic moment of Cr 2+ ion is:
- A. 4.90 BM
- B. 5.92 BM
- C. 2.84 BM
- D. 3.87 BM
Answer: A. 4.90 BM
Cr atom is [Ar] 3d5 4s1. Cr 2+ is [Ar] 3d4. It has 4 unpaired electrons. Magnetic moment = sqrt(n(n+2)) = sqrt(4(6)) = sqrt(24) ≈ 4.90 BM.
Cr atom is [Ar] 3d5 4s1. Cr 2+ is [Ar] 3d4. It has 4 unpaired electrons. Magnetic moment = sqrt(n(n+2)) = sqrt(4(6)) = sqrt(24) ≈ 4.90 BM.
Calculated spin-only magnetic moment of Cr2+ ion is:
- A. 4.90 BM
- B. 5.92 BM
- C. 2.84 BM
- D. 3.87 BM
Answer: A. 4.90 BM
Cr2+ has a d4 configuration. The number of unpaired electrons (n) = 4. Magnetic moment = sqrt(n(n+2)) = sqrt(4(6)) = sqrt(24) ≈ 4.90 BM.
Cr2+ has a d4 configuration. The number of unpaired electrons (n) = 4. Magnetic moment = sqrt(n(n+2)) = sqrt(4(6)) = sqrt(24) ≈ 4.90 BM.
Given below are two statements: Statement I: Ferromagnetism is considered as an extreme form of paramagnetism. Statement II: The number of unpaired electrons in a Cr²⁺ ion (Z=24) is the same as that of a Nd³⁺ ion (Z=60).
- A. Both Statement I and Statement II are true
- B. Both Statement I and Statement II are false
- C. Statement I is true but Statement II is false
- D. Statement I is false but Statement II is true
Answer: C. Statement I is true but Statement II is false
Cr²⁺: [Ar] 3d⁴ (4 unpaired). Nd³⁺: [Xe] 4f³ (3 unpaired). Statement II is false.
Cr²⁺: [Ar] 3d⁴ (4 unpaired). Nd³⁺: [Xe] 4f³ (3 unpaired). Statement II is false.
The electronic configurations of Eu (Atomic No. 63), Gd (Atomic No. 64) and Tb (Atomic No. 65) are:
- A. [Xe]4f6 5d1 6s2, [Xe]4f7 5d1 6s2 and [Xe]4f9 6s2
- B. [Xe]4f6 5d1 6s2, [Xe]4f7 5d1 6s2 and [Xe]4f8 5d1 6s2
- C. [Xe]4f7 6s2, [Xe]4f7 5d1 6s2 and [Xe]4f9 6s2
- D. [Xe]4f7 6s2, [Xe]4f8 6s2 and [Xe]4f8 5d1 6s2
Answer: C. [Xe]4f7 6s2, [Xe]4f7 5d1 6s2 and [Xe]4f9 6s2
Eu (63) is [Xe]4f7 6s2 (half-filled f-subshell is stable), Gd (64) is [Xe]4f7 5d1 6s2 (extra stability of half-filled f-subshell), and Tb (65) is [Xe]4f9 6s2.
Eu (63) is [Xe]4f7 6s2 (half-filled f-subshell is stable), Gd (64) is [Xe]4f7 5d1 6s2 (extra stability of half-filled f-subshell), and Tb (65) is [Xe]4f9 6s2.
Match items of Column I with the items of Column II and assign the correct code: Column I Column II (a) Cyanide process (i) Ultrapure Ge (b) Froth floatation process (ii) Dressing of Zns (c) Electrolytic reduction (iii) Extraction of Al (d) Zone refining (iv) Extraction of Au (v) Purification of Ni
- A. (1) (ii) (iii) (i) (v)
- B. (2) (i) (ii) (iii) (iv)
- C. (3) (iii) (iv) (v) (i)
- D. (4) (iv) (ii) (iii) (i)
Answer: D. (4) (iv) (ii) (iii) (i)
Cyanide process is used for Au extraction (iv), Froth floatation for ZnS (ii), Electrolytic reduction for Al (iii), and Zone refining for high-purity Ge (i).
Cyanide process is used for Au extraction (iv), Froth floatation for ZnS (ii), Electrolytic reduction for Al (iii), and Zone refining for high-purity Ge (i).