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d- and f-Block Elements · Question 20

JEE Main 2026 (Online) 22nd January Evening ShiftMCQMedium📈 Topic in 13% papers+4−1
1

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

  1. Statement I is true but Statement II is false
  2. Both Statement I and Statement II are true
  3. Both Statement I and Statement II are false
  4. Statement I is false but Statement II is true

Answer

(1) Statement I is true but Statement II is false

Solution

As per NCERT, ionization enthalpies ( kJ mol-1):

Cr: iH1 = 653, iH2 = 1592, iH3 = 2987

Mn: iH1 = 717, iH2 = 1509, iH3 = 3248

Statement I: 653 < 717; Mn (3d5 4s2) loses an electron from a filled 4s orbital of a stable configuration. Statement I is true.

Statement II: iH2 of Cr > Mn (Cr+ is 3d5, stable), but iH3 of Cr < Mn ( Mn2+ is the stable 3d5, so removing the third electron from Mn is harder). Statement II is false.

Answer: (1)

JEE Main 2026 (Online) 22nd January Evening Shift

Keep practising — d- and f-Block Elements

2

Among the following oxides of 3d elements, the number of mixed oxides are . Ti2O3, V2O4, Cr2O3, Mn3O4, Fe3O4, Fe2O3, Co3O4

JEE Main 2026 (Online) 22nd January Evening Shift
3

MnO42-, in acidic medium, disproportionates to :

  1. MnO4- and MnO
  2. MnO4- and MnO2
  3. Mn2O7 and MnO2
  4. Mn2O7 and MnO
JEE Main 2026 (Online) 21st January Morning Shift
4

Consider the following reactions : NaCl + K2Cr2O7 + H2SO4 A + KHSO4 + NaHSO4 + H2O A + NaOH B + NaCl + H2O B + H2SO4 + H2O2 C + Na2SO4 + H2O In the product 'C', 'X' is the number of O22- units, 'Y' is the total number of oxygen atoms present and 'Z' is the oxidation state of Cr. The value of X + Y + Z is .

JEE Main 2026 (Online) 21st January Morning Shift
5

Given below are some of the statements about Mn and Mn2O7. Identify the correct statements. Choose the correct answer from the options given below :

  1. A, B, C and D
  2. A, B and D Only
  3. A, B and C Only
  4. A, C and D Only
JEE Main 2026 (Online) 21st January Evening Shift
6

The correct decreasing order of spin only magnetic moment values (BM) of Cu+, Cu2+, Cr2+ and Cr3+ ions is :

  1. Cr3+ > Cr2+ > Cu+ > Cu2+
  2. Cu+ > Cu2+ > Cr3+ > Cr2+
  3. Cr2+ > Cr3+ > Cu2+ > Cu+
  4. Cu2+ > Cu+ > Cr2+ > Cr3+
JEE Main 2025 (Online) 8th April Evening Shift
7

The first transition series metal 'M' has the highest enthalpy of atomisation in its series. One of its aquated ions ( Mn+) exists in green colour. The nature of the oxide formed by the above Mn+ ion is:

  1. basic
  2. neutral
  3. amphoteric
  4. acidic
JEE Main 2025 (Online) 7th April Morning Shift
8

The number of valence electrons present in the metal among Cr, Co, Fe and Ni which has the lowest enthalpy of atomisation is :

  1. 10
  2. 6
  3. 9
  4. 8
JEE Main 2025 (Online) 7th April Morning Shift
9

'X' is the number of acidic oxides among VO2, V2O3, CrO3, V2O5 and Mn2O7. The primary valency of cobalt in [Co(H2NCH2CH2NH2)3]2(SO4)3 is Y. The value of X + Y is .

  1. 3
  2. 4
  3. 2
  4. 5
JEE Main 2025 (Online) 7th April Evening Shift
10

Pair of transition metal ions having the same number of unpaired electrons is

  1. Ti3+, Mn2+
  2. Ti2+, Co2+
  3. Fe3+, Cr2+
  4. V2+, Co2+
JEE Main 2025 (Online) 4th April Morning Shift
11

KMnO4 acts as an oxidising agent in acidic medium. 'X' is the difference between the oxidation states of Mn in reactant and product. 'Y' is the number of 'd' electrons present in the brown red precipitate formed at the end of the acetate ion test with neutral ferric chloride. The value of X + Y is .

JEE Main 2025 (Online) 4th April Morning Shift

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