d- and f-Block Elements · Question 35

Magnetic moment 2.83 BM is given by which of the following ions? (At. nos. Ti = 22, Cr = 24, Mn = 25, Ni = 28)

1. Ti3+
2. Ni2+
3. Cr3+
4. Mn2+

Reason of lanthanoid contraction is

1. negligible screening effect of 'f'-orbitals
2. increasing nuclear charge
3. decreasing nuclear charge
4. decreasing screening effect.

KMnO4 can be prepared from K2MnO4 as per the reaction, 3MnO42- + 2H2O 2MnO4- + MnO2 + 4OH- The reaction can go to completion by removing OH- ions by adding

1. CO2
2. SO2
3. HCl
4. KOH

Which of the following does not give oxygen on heating?

1. K2Cr2O7
2. (NH4)2Cr2O7
3. KClO3
4. Zn(ClO3)2

Which of the following statements about the interstitial compounds is incorrect?

1. They are much harder than the pure metal.
2. They have higher melting points than the pure metal.
3. They retain metallic conductivity.
4. They are chemically reactive.

Which of the following lanthanoid ions is diamagnetic? (At. nos. Ce = 58, Sm = 62, Eu = 63, Yb = 70)

1. Eu2+
2. Yb2+
3. Ce2+
4. Sm2+

The outer electronic configuration of Gd (At. No. 64) is

1. 4f5 5d4 6s1
2. 4f7 5d1 6s2
3. 4f3 5d5 6s2
4. 4f4 5d5 6s1

Sc (Z = 21) is a transition element but Zn (Z = 30) is not because

1. both Sc3+ and Zn2+ ions are colourless and form white compounds.
2. in case of Sc, 3d orbitals are partially filled but in Zn these are filled.
3. last electron is assumed to be added to 4s level in case of Zn.
4. both Sc and Zn do not exhibit variable oxidation states.

The catalytic activity of transition metals and their compounds is ascribed mainly to

1. their magnetic behaviour
2. their unfilled d-orbitals
3. their ability to adopt variable oxidation states
4. their chemical reactivity

Which of the following exhibits only + 3 oxidation state?

1. U
2. Th
3. Ac
4. Pa