JEE Chemistry The D and F Block Elements MCQs Set 16

Answer: (c) +2

Explanation:
1. Cu(II) is the most stable state in aqueous solution; most common salts are of Cu(II).

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) \( \ce{Fe - Hg} \)

Explanation:
1. Iron does not form an amalgam or alloy with mercury, which is why mercury is stored in iron flasks.
2. Zn-Cu (brass), Fe-C (steel) and Na-Hg (amalgam) all form.

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) \( \ce{ZnSO4.7H2O} \)

Explanation:
1. Isomorphous substances have similar formula type and crystal form; \( \ce{FeSO4.7H2O} \) and \( \ce{ZnSO4.7H2O} \) are both heptahydrate sulphates of M(II) of similar size.

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) galvanisation

Explanation:
1. Coating iron with zinc is called galvanisation.

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) \( \ce{Zn} \)

Explanation:
1. \( \ce{Zn + 2NaOH -> Na2ZnO2 + H2} \).
2. Fe, Cu and Ag do not react with alkali.

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) silver bromide

Explanation:
1. The light-sensitive layer is silver bromide in gelatin.

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. Copper lies below hydrogen in the electrochemical series and is not attacked by non-oxidising acids, because the free energy change for the process is positive.
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: (a) Both A and R are true and R is the correct explanation of A

Explanation:
1. On exposure to light \( \ce{2AgBr -> 2Ag + Br2} \), forming the latent image.
2. This photosensitivity is the reason for its use.

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) greater solubility of the impurity in the molten state than in the solid

Explanation:
1. The impurities stay dissolved in the moving molten zone and are swept to one end.

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) silver

Explanation:
1. Argentocyanide, \( \ce{K[Ag(CN)2]} \), is the soluble silver complex.

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) Both A and R are true and R is the correct explanation of A

Explanation:
1. \( \ce{Fe^{2+}} \) is 3d6, which in the free ion (or a high-spin complex) has 4 unpaired electrons.
2. The unpaired electrons are the cause of paramagnetism, so R explains A.

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) treating argentite with NaCN solution followed by metal displacement with zinc

Explanation:
1. Argentite is leached with NaCN to give \( \ce{[Ag(CN)2]^-} \) and silver is precipitated with zinc dust.

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 normal spinel compound

Explanation:
1. In \( \ce{ZnFe2O4} \) divalent Zn occupies tetrahedral holes and trivalent Fe the octahedral holes, which is a normal spinel.

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) Zn and Cu

Explanation:
1. Brass is copper with about 20 to 40 percent zinc; bronze is Cu with Sn.

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) \( \ce{Cu} \)

Explanation:
1. All three are copper alloys; zinc is absent from bronze.

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) \( \ce{Cu2[Fe(CN)6]} \)

Explanation:
1. \( \ce{2CuSO4 + K4[Fe(CN)6] -> Cu2[Fe(CN)6] + 2K2SO4} \).

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) its Curie point

Explanation:
1. Ferromagnetism disappears above the Curie temperature (about 1043 K for iron).
2. At 1000 K iron is still ferromagnetic and the other two temperatures are much higher.

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) \( \ce{Cu} \)

Explanation:
1. Ca and Li reduce cold water, Fe reduces steam, and Cu is below hydrogen so it does not reduce 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: (b) \( \ce{3Fe + 4H2O -> Fe3O4 + 4H2} \)

Explanation:
1. Red-hot iron and steam give magnetic oxide \( \ce{Fe3O4} \) and hydrogen; this is the only balanced equation among the options.

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) \( \ce{Mn} \)

Explanation:
1. Manganese steel (about 12-14 percent Mn) is extremely hard and tough and is used for these purposes.

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) measuring the solid-state magnetic moment

Explanation:
1. Fe(II) low spin (d6) with \( \ce{NO^+} \) is diamagnetic, while Fe(III) with neutral NO would be paramagnetic.
2. The composition (Fe content, CN content) is the same for both, so only the magnetic moment differs.

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) copper sulphate solution reacts with \( \ce{K4[Fe(CN)6]} \)

Explanation:
1. Copper sulphate with potassium ferrocyanide gives a chocolate-brown precipitate of \( \ce{Cu2[Fe(CN)6]} \).
2. The others give deep blue \( \ce{[Cu(NH3)4]^{2+}} \), Prussian blue and blue aqueous Cu(II).

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) \( \ce{K2SO4 + Cu2I2 + I2} \)

Explanation:
1. \( \ce{Cu^{2+}} \) oxidises iodide to iodine and is reduced to Cu(I), which precipitates as CuI.
2. \( \ce{2CuSO4 + 4KI -> Cu2I2 + 2K2SO4 + I2} \).

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) hard and brittle

Explanation:
1. Sudden cooling (quenching) makes steel hard and brittle.

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) heating steel to bright redness and then cooling slowly

Explanation:
1. Annealing is slow cooling after strong heating, which softens the steel.

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) \( \ce{[Fe(H2O)5NO]SO4} \)

Explanation:
1. Nitrate is reduced to NO, which coordinates to Fe(II): \( \ce{[Fe(H2O)6]^{2+} + NO -> [Fe(H2O)5(NO)]^{2+} + H2O} \).
2. The brown ring is pentaaquanitrosyliron(II) sulphate.

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.