d- and f-Block Elements

Acidified K2Cr2O7 solution turns green when Na2SO3 is added to it. This is due to the formation of

1. Cr2(SO4)3
2. CrO42-
3. Cr2(SO3)3
4. CrSO4

Which of the following oxidation states is the most common among the lanthanoids?

1. 4
2. 2
3. 5
4. 3

Which of the following ions will exhibit colour in aqueous solutions?

1. La3+ (Z = 57)
2. Ti3+ (Z = 22)
3. Lu3+ (Z = 71)
4. Sc3+ (Z = 21)

Which of the following ions has electronic configuration [Ar]3d6? (At. nos. Mn = 25, Fe = 26, Co = 27, Ni = 28)

1. Ni3+
2. Mn3+
3. Fe3+
4. Co3+

Which of the following pairs has the same size?

1. Fe2+, Ni2+
2. Zr4+, Ti4+
3. Zr4+, Hf4+
4. Zn2+, Hf4+

Which one of the elements with the following outer orbital configurations may exhibit the largest number of oxidation states?

1. 3d54s1
2. 3d54s2
3. 3d24s2
4. 3d34s2

Out of TiF62-, CoF63-, Cu2Cl2 and NiCl42- (Z of Ti = 22, Co = 27, Cu = 29, Ni = 28) the colourless species are

1. Cu2Cl2 and NiCl42-
2. TiF62- and Cu2Cl2
3. CoF63- and NiCl42-
4. TiF62- and CoF63-

The correct order of decreasing second ionisation enthalpy of Ti(22), V(23), Cr(24) and Mn(25) is

1. Mn > Cr > Ti > V
2. Ti > V > Cr > Mn
3. Cr > Mn > V > Ti
4. V > Mn > Cr > Ti

Which one of the following ions is the most stable in aqueous solution? (At. No. Ti = 22, V = 23, Cr = 24, Mn = 25)

1. V3+
2. Ti3+
3. Mn3+
4. Cr3+

Identify the incorrect statement among the following:

1. Lanthanoid contraction is the accumulation of successive shrinkages.
2. As a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of elements.
3. Shielding power of 4f electrons is quite weak.
4. There is a decrease in the radii of the atoms or ions as one proceeds from La to Lu.