JEE Chemistry The D and F Block Elements MCQs Set 13

Answer: (b) f-block element

Explanation:
1. Europium (Z = 63) is a lanthanide, which belongs to the f-block.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (b) zinc

Explanation:
1. Brass is an alloy of copper and zinc.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) Cr

Explanation:
1. Cr has six unpaired electrons (3d⁵ 4s¹) available for metallic bonding, the maximum in the series.
2. So it has the strongest metallic bond among these.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) \( \ce{Zn^{2+}} \)

Explanation:
1. \( \ce{Zn^{2+}} \) is 3d¹⁰, so no d-d transition is possible.
2. The others have partly filled d subshells (3d⁹, 3d⁵, 3d¹).

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) oxidation of Cu

Explanation:
1. \( \ce{Cu + 2Ag^+ -> Cu^{2+} + 2Ag} \).
2. Copper is oxidised to blue \( \ce{Cu^{2+}} \) while silver ions are reduced.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (b) Eu

Explanation:
1. Europium has the configuration [Xe] 4f⁷ 6s²; losing two electrons gives the stable half-filled 4f⁷ ion \( \ce{Eu^{2+}} \).
2. So both +2 and +3 are common.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) 0

Explanation:
1. \( \ce{Zn^{2+}} \) is 3d¹⁰, so all electrons are paired.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (b) scandium

Explanation:
1. The d-block begins when the 3d subshell starts filling, at scandium (Z = 21).

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) 3d⁵ 4s⁰

Explanation:
1. Mn is [Ar] 3d⁵ 4s². Both 4s electrons are removed first, giving [Ar] 3d⁵.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) most of the transition elements show only one valence state

Explanation:
1. Transition elements typically show several oxidation states because (n-1)d and ns energies are close.
2. So the statement about a single valence state is the false one.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) Cr

Explanation:
1. Cr can use all six valence electrons, reaching +6 (chromates).
2. Co, Ni and Cu show at most about +4, +4 and +3 respectively.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) Wood's metal

Explanation:
1. Wood's metal (Bi, Pb, Sn, Cd) melts at about 70 degrees Celsius, below the boiling point of water.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) Hg

Explanation:
1. Hg has a positive standard reduction potential (+0.85 V), so it cannot displace hydrogen.
2. Al, Pb and Ba lie above hydrogen in the series.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) high charge/size ratio and vacant d-orbitals

Explanation:
1. A high charge-to-size ratio attracts ligands strongly and vacant d orbitals accept lone pairs.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) they have one or more unpaired d-electrons

Explanation:
1. Paramagnetism arises from unpaired electrons; in these ions they are in the d subshell.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) f-orbital electrons are poor shielders of nuclear charge

Explanation:
1. The 4f electrons shield the nuclear charge poorly, so the effective nuclear charge rises along the series.
2. The outer electrons are pulled in, and atomic and ionic radii shrink steadily.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) Fe

Explanation:
1. Of these, Fe has the most negative standard reduction potential (\( E^\circ = -0.44 \) V), so it is the most reactive.
2. Pt is a noble metal.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) Fe

Explanation:
1. Among the three ferromagnetic metals Fe, Co and Ni, iron has the strongest ferromagnetism; Pt is not ferromagnetic.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) all of these

Explanation:
1. Small atoms such as H, B, C and N fit into the interstices of transition metal lattices, giving interstitial compounds with all three metals.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (b) Pt

Explanation:
1. Platinum is a very unreactive noble metal and occurs native.
2. Fe, Co and Ni occur as ores.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) \( \ce{Zn^{2+}} \)

Explanation:
1. \( \ce{Zn^{2+}} \) is [Ar] 3d¹⁰.
2. \( \ce{Cu^{2+}} \) is 3d⁹, while \( \ce{Cd^{2+}} \) and \( \ce{Hg^{2+}} \) are 4d¹⁰ and 5d¹⁰.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) \( \ce{Ti^{4+}} \)

Explanation:
1. \( \ce{Ti^{4+}} \) has lost all four valence electrons from [Ar] 3d² 4s² and is 3d⁰.
2. \( \ce{Sc^{2+}} \) is 3d¹, \( \ce{Zn^{2+}} \) is 3d¹⁰ and \( \ce{Pd^{2+}} \) is 4d⁸.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) both (a) and (b)

Explanation:
1. The lanthanides (Z = 58-71) and actinides (Z = 90-103) together form the f-block.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) Cu > Ni > Zn > Sc

Explanation:
1. Densities in g/cm³ are approximately Cu 8.96, Ni 8.91, Zn 7.14 and Sc 2.99.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) blue

Explanation:
1. \( \ce{[Cu(H2O)4]^{2+}} \) absorbs in the red-orange region and appears blue.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) Cu

Explanation:
1. The weakest reducing agent is the species with the most positive \( E^\circ \) for its oxidised form.
2. Cu (\( +0.34 \) V) is far less reducing than Zn, \( \ce{H2} \) and Li.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) uranium

Explanation:
1. Atomic masses: U 238, Ra 226, Pb 207, Hg 201.
2. Uranium is the heaviest.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.