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d- and f-Block Elements · Question 59

AIPMT 2007MCQMedium📈 Topic in 12% papers+4−1
1

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+

Answer

(4) Cr3+

Solution

Configurations: Ti3+: 3d1, V3+: 3d2, Cr3+: 3d3, Mn3+: 3d4

Ti3+ and V3+ are easily oxidised (reducing ions) to higher, more stable states.

Mn3+: E (Mn3+/Mn2+) = +1.57 V ⇒ strongly oxidising; it gains an electron to give the stable d5 Mn2+ and disproportionates in water.

Cr3+: E (Cr3+/Cr2+) = -0.41 V ⇒ Cr2+ is reducing and changes to Cr3+.

As per NCERT, Cr3+ (d3) has a half-filled t2g level in water, which gives it extra stability.

∴ Cr3+ is the most stable ion in aqueous solution.

Answer: (4)

AIPMT 2007

Keep practising — d- and f-Block Elements

2

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.
AIPMT 2007
3

In which of the following pairs are both the ions coloured in aqueous solution? (At. no. : Sc = 21, Ti = 22, Ni = 28, Cu = 29, Co = 27)

  1. Ni2+, Cu+
  2. Ni2+, Ti3+
  3. Sc3+, Ti3+
  4. Sc3+, Co2+.
AIPMT 2006
4

Copper sulphate dissolves in excess of KCN to give

  1. Cu(CN)2
  2. CuCN
  3. [Cu(CN)4]3-
  4. [Cu(CN)4]2-
AIPMT 2006
5

More number of oxidation states are exhibited by the actinoids than by the lanthanoids. The main reason for this is

  1. more active nature of the actinoids
  2. more energy difference between 5f and 6d orbitals than that between 4f and 5d orbitals
  3. lesser energy difference between 5f and 6d orbitals than that between 4f and 5d orbitals
  4. greater metallic character of the lanthanoids than that of the corresponding actinoids.
AIPMT 2006
6

More number of oxidation states are exhibited by the actinoids than by the lanthanoids. The main reason for this is

  1. more active nature of the actinoids
  2. more energy difference between 5f and 6d orbitals than that between 4f and 5d orbitals
  3. lesser energy difference between 5f and 6d orbitals than that between 4f and 5d orbitals
  4. greater metallic character of the lanthanoids than that of the corresponding actinoids.
AIPMT 2005
7

The number of moles of KMnO4 reduced by one mole of KI in alkaline medium is

  1. one
  2. two
  3. five
  4. one fifth
AIPMT 2005
8

Four successive members of the first row transition elements are listed below with their atomic numbers. Which one of them is expected to have the highest third ionisation enthalpy?

  1. Vanadium (Z = 23)
  2. Chromium (Z = 24)
  3. Manganese (Z = 25)
  4. Iron (Z = 26)
AIPMT 2005
9

The aqueous solution containing which one of the following ions will be colourless? (Atomic number : Sc = 21, Fe = 26, Ti = 22, Mn = 25)

  1. Sc3+
  2. Fe2+
  3. Ti3+
  4. Mn2+
AIPMT 2005
10

Among K, Ca, Fe and Zn, the element which can form more than one binary compound with chlorine is

  1. Fe
  2. Zn
  3. K
  4. Ca
AIPMT 2004
11

Among the following series of transition metal ions, the one where all metal ions have 3d2 electronic configuration is [At. Nos. Ti = 22, V = 23, Cr = 24, Mn = 25]

  1. Ti3+, V2+, Cr3+, Mn4+
  2. Ti+, V4+, Cr6+, Mn7+
  3. Ti4+, V3+, Cr2+, Mn3+
  4. Ti2+, V3+, Cr4+, Mn5+
AIPMT 2004

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