The d- and f-Block Elements Chapter-Wise Test 8

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which of the following is a characteristic property of f-block elements?

Lanthanoid contraction is the gradual decrease in atomic/ionic radii across the lanthanoid series.

Variable oxidation states
Lanthanoid contraction
High volatility
Formation of colored ions
2

What is the product when K2Cr2O7 reacts with H2S in acidic medium?

Cr2O72– oxidizes H2S to S (yellow precipitate) and reduces to Cr3+ (green).

CrO42– + SO2
Cr2+ + H2SO4
CrO2 + H2O
Cr3+ + S
4

What is the effect of lanthanoid contraction on the atomic sizes of post-lanthanoid elements?

Lanthanoid contraction causes similar atomic sizes of 4d and 5d transition elements.

Increases their sizes
No effect
Makes 4d and 5d elements similar in size
Decreases their densities
3

Which of the following is a consequence of lanthanoid contraction?

Lanthanoid contraction causes similar atomic radii of Zr (160 pm) and Hf (159 pm), making their separation difficult.

Increase in atomic radii across the series
Decrease in density of lanthanoids
Similar sizes of Zr and Hf
Increase in ionization energy
3

Which of the following represents the reaction of K2Cr2O7 with FeSO4 in acidic medium?

Cr2O72- + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O

Oxidation of Fe2+ to Fe3+
Reduction of Fe3+ to Fe2+
Formation of FeCr2O4
No reaction occurs
1

Which of the following is NOT a property of transition metals?

Transition metals form interstitial compounds, not intermetallic compounds (alloys are different).

Formation of colored ions
Catalytic activity
Formation of intermetallic compounds
Paramagnetism
3

Which of the following transition metals has the highest enthalpy of atomization?

Tungsten (W) has the highest enthalpy of atomization in the 5d series due to strong metallic bonding.

Cr
W
Fe
Ni
2

What is the product when acidified KMnO4 reacts with Fe2+?

MnO4– oxidizes Fe2+ to Fe3+ and itself reduces to Mn2+.

Fe3+ + Mn2+
Fe + MnO2
Fe3+ + MnO2
Fe + Mn2+
1

Which lanthanoid exhibits +2 oxidation state due to f7 configuration?

Eu2+ (Europium) has a stable half-filled f7 configuration.

Ce
Eu
Gd
Lu
2

What is the primary reason for the variable oxidation states in transition elements?

Comparable energies of (n-1)d and ns orbitals allow for variable electron loss.

Small atomic size
High ionization energy
Comparable energies of (n-1)d and ns orbitals
Presence of f-electrons
3

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