JEE Chemistry The D and F Block Elements MCQs Set 19

Answer: (b) 25

Explanation:
1. The configuration is \( 3s^2 3p^6 3d^5 4s^2 \) on top of \( 1s^2 2s^2 2p^6 \), giving 2 + 8 + 8 + 5 + 2 = 25 electrons.
2. The neutral atom (manganese) has 25 protons.

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) \( \ce{CdS} \)

Explanation:
1. CdS is yellow, ZnS white, CuS and CoS black.

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) a base

Explanation:
1. In low oxidation states the metal oxides and hydroxides are basic; the acidic character increases with oxidation state.

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) Wrought iron

Explanation:
1. Wrought iron has only about 0.1-0.25 percent carbon.

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) \( \ce{Cu^{2+}} \)

Explanation:
1. Stability of complexes of the 3d M(II) ions follows the Irving-Williams order, rising to a maximum at copper: \( \ce{Mn^{2+} < Fe^{2+} < Co^{2+} < Ni^{2+} < Cu^{2+}} \).

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) Phosphorus impurity cannot be removed by this process

Explanation:
1. The basic lining and limestone flux combine with phosphorus oxide as slag, so phosphorus can be removed.
2. Statement (b) is therefore wrong.

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) \( \ce{PbO2} \)

Explanation:
1. Only a strong oxidant (in acid) can oxidise Mn(II) to Mn(VII): \( \ce{2Mn^{2+} + 5PbO2 + 4H^+ -> 2MnO4^- + 5Pb^{2+} + 2H2O} \).
2. The other options are reducing agents or too weak.

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) \( \ce{Ag} \)

Explanation:
1. \( \ce{2AgNO3 -> 2Ag + 2NO2 + O2} \).

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) anhydrous \( \ce{ZnCl2} \) + conc. HCl

Explanation:
1. Lucas reagent (anhydrous zinc chloride in conc. HCl) distinguishes primary, secondary and tertiary alcohols.

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) Low electrical conductivity

Explanation:
1. Copper is an excellent electrical conductor, second only to silver.

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) \( \ce{Sn} \)

Explanation:
1. Bronze is an alloy of copper and tin.

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) 3/5

Explanation:
1. One mole of \( \ce{FeC2O4} \) gives 3 mol of electrons (Fe(II) to Fe(III): 1; oxalate to 2CO2: 2).
2. One mole of permanganate accepts 5 mol of electrons, so 3/5 mol is needed.

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) \( sp^3 \)

Explanation:
1. Nickel is 0 in this complex (3d8 4s2 rearranges to 3d10).
2. With CO as strong-field ligand all ten electrons pair in 3d, and one 4s and three 4p orbitals hybridise: \( sp^3 \), tetrahedral.

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) sulphur dioxide

Explanation:
1. Dissolved \( \ce{SO2} \) is released on solidification and makes blisters on the surface.

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) violet

Explanation:
1. The hydrated ion \( \ce{[Fe(H2O)6]^{3+}} \) in this alum gives pale violet crystals.

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. Zinc is amphoteric: \( \ce{Zn + 2HCl -> ZnCl2 + H2} \) and \( \ce{Zn + 2NaOH -> Na2ZnO2 + H2} \).

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) \( \ce{Na[Ag(CN)2]} \)

Explanation:
1. \( \ce{4Ag + 8NaCN + 2H2O + O2 -> 4Na[Ag(CN)2] + 4NaOH} \).
2. Silver is +1 and the complex ion is \( \ce{[Ag(CN)2]^-} \), so only one sodium is needed.

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) A is false

Explanation:
1. The assertion is reversed: \( \ce{Cu^+} \) is 3d10 (no unpaired electrons) and \( \ce{Cu^{2+}} \) is 3d9 (one unpaired electron).
2. So A is false (the reason is true).

Teacher's Note:
1. Link each compound to its colour, oxidation state and reaction medium; these facts are asked repeatedly.
2. For redox questions, count the electrons exchanged per formula unit before choosing an option.

Answer: (b) wrought iron

Explanation:
1. Wrought iron is the purest form of iron; low carbon content gives the highest melting point (about 1500 C).

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) A is false

Explanation:
1. \( \ce{FeCl3} \) hydrolyses to give \( \ce{Fe(OH)3} \) and HCl, so the solution is acidic.
2. A is false.

Teacher's Note:
1. Link each compound to its colour, oxidation state and reaction medium; these facts are asked repeatedly.
2. For redox questions, count the electrons exchanged per formula unit before choosing an option.

Answer: (d) silver

Explanation:
1. Silver has the highest electrical conductivity of all 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: (c) \( \ce{Co} \)

Explanation:
1. \( \ce{CoCl2} \) (3d7) is blue when anhydrous and pink when hydrated; AgCl, \( \ce{HgCl2} \) and \( \ce{ZnCl2} \) are white.

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) reduction of \( \ce{Cu^{2+}} \)

Explanation:
1. \( \ce{Fe + Cu^{2+} -> Fe^{2+} + Cu} \).

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) \( \ce{VOSO4} \)

Explanation:
1. \( \ce{VO^{2+}} \) contains V(IV), 3d1: one unpaired electron and a blue colour.
2. Dichromate is d0 and diamagnetic, Ti(IV) is d0 and colourless, and Cu(I) is d10 and colourless.

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) silver nitrate

Explanation:
1. Fused silver nitrate cast into sticks is lunar caustic, used to cauterise tissue.

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) \( \ce{Ag2S} \)

Explanation:
1. Silver sulphide has the lowest solubility product (about \( 10^{-50} \)) 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.