AIIMS Chemistry The D And Fblock Elements Class 12 Questions

The electron configuration of Yb⁺² is [Xe]₄f¹⁴5d⁰6s⁰ and the electron configuration of Gd⁺² is [Xe]₄f⁷5d¹6s⁰ So, Yb⁺² is more stable in compare to Gd⁺² due to the fully filled stabilized electron configuration. So, the assertion is true but the reason is false.

The basic strength of hydroxides is La(OH)₃ > Lu(OH)₃. Due to lanthanide contraction, size of M³⁺ ions decrease and there is an increase in the covalent character of M⁻OH bond.

In the equation, $$4\text{M} + 8\text{CN}^- + 2\text{H}_2\text{O} + \text{O}_2 \rightarrow 4[\text{M}(\text{CN})_2]^- + 4\text{OH}^-$$ Identify the metal (M)

Among the metals Fe, Zn, Pb, Ag and Pt, which do not give a metal nitrate on treatment with concentrated HNO₃?

Assertion (A) In any transition series, the number of unpaired electrons first increases, afterward decrease. Reason (R) In any transition series, the number of unpaired electrons first increases, afterward decrease.

Which is not stable under ambient condition?

Assertion: $\text{Ce}^{4+}$ is used as an oxidising agent in volumetric analysis. Reason: $\text{Ce}^{4+}$ has the tendency of attaining +3 oxidation state.

Assertion: $\text{La}(\text{OH})_3$ is more basic than $\text{Lu}(\text{OH})_3$. Reason: Size of $\text{Lu}^{3+}$ increases and shows more covalent character.

What are constituents of 'Mischmetal'?

Assertion: Transition metals are poor reducing agents. Reason: Transition metals form numerous alloys with other metals.

Which of the element shows +4 oxidation state?

Assertion : Magnetic moment of Dy is the highest among the lanthanoids. Reason : Orbital motion contributes magnetic moment.

Given below, catalyst and corresponding process/reaction are matched. The mismatch is

Assertion : K₂Cr₂O₇ is used as primary standard in volumetric analysis. Reason : It has a good solubility in water.

Among the following pairs of ions, the lower oxidation state in aqueous solution is more stable than the other, in

Assertion : The free gaseous Cr atom has six unpaired electrons. Reason : Half-filled s orbital has greater stability.

The colourless species is

Lanthanide for which +II and +III oxidation states are common is

Assertion : Cuprous ion (Cu⁺) is colourless whereas cupric ion (Cu²⁺) is blue in the aqueous solution. Reason : Cuprous ion (Cu⁺) has unpaired electrons while cupric ion (Cu²⁺) does not.

Which of the following has highest second ionization energy?

Which of the following is the correct sequence of atomic weights of the given elements ?

In dichromate dimer