d- and f-Block Elements

Which of the statements is not true?

1. On passing H2S through acidified K2Cr2O7 solution, a milky colour is observed.
2. Na2Cr2O7 is preferred over K2Cr2O7 in volumetric analysis.
3. K2Cr2O7 solution in acidic medium is orange.
4. K2Cr2O7 solution becomes yellow on increasing the pH beyond 7.

For the four successive transition elements (Cr, Mn, Fe and Co), the stability of +2 oxidation state will be there in which of the following order? (At. nos. Cr = 24, Mn = 25, Fe = 26, Co = 27)

1. Mn > Fe > Cr > Co
2. Fe > Mn > Co > Cr
3. Co > Mn > Fe > Cr
4. Cr > Mn > Co > Fe

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