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d- and f-Block Elements · Question 27

JEE Main 2025 (Online) 7th April Morning ShiftMCQEasy📈 Topic in 13% papers+4−1
1

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

Answer

(2) 6

Solution

As per NCERT, aH ( kJ mol-1): Cr 397, Fe 416, Co 425, Ni 430

Lowest for Cr

Cr (Z = 24): [Ar] 3d5 4s1

Valence electrons = 5 (3d) + 1 (4s) = 6

Answer: (2)

JEE Main 2025 (Online) 7th April Morning Shift

Keep practising — d- and f-Block Elements

2

'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
3

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
4

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
5

The incorrect relationship in the following pairs in relation to ionisation enthalpies is :

  1. Mn2+ < Fe2+
  2. Mn+ < Mn2+
  3. Mn+ < Cr+
  4. Fe2+ < Fe3+
JEE Main 2025 (Online) 4th April Evening Shift
6

The metal ions that have the calculated spin-only magnetic moment value of 4.9 B.M. are : Choose the correct answer from the options given below:

  1. A, D and E Only
  2. A, B and E Only
  3. A, C and E Only
  4. B and E Only
JEE Main 2025 (Online) 3rd April Morning Shift
7

Consider the following reactions A + Little amountNaCl + H2SO4 CrO2Cl2 + Side Products CrO2Cl2(Vapour) + NaOH B + NaCl + H2O B + H+ C + H2O The number of terminal 'O' present in the compound 'C' is

JEE Main 2025 (Online) 3rd April Morning Shift
8

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
JEE Main 2025 (Online) 3rd April Evening Shift
9

Among Sc, Mn, Co and Cu, identify the element with highest enthalpy of atomisation. The spin only magnetic moment value of that element in its +2 oxidation state is BM (in nearest integer).

JEE Main 2025 (Online) 3rd April Evening Shift
10

The spin-only magnetic moment value of Mn+ ion formed among Ni, Zn, Mn and Cu that has the least enthalpy of atomisation is . (in nearest integer) Here n is equal to the number of diamagnetic complexes among K2[NiCl4], [Zn(H2O)6]Cl2, K3[Mn(CN)6] and [Cu(PPh3)3I]

JEE Main 2025 (Online) 2nd April Evening Shift
11

The correct option with order of melting points of the pairs (Mn, Fe), (Tc, Ru) and (Re, Os) is :

  1. Fe < Mn, Ru < Tc and Re < Os
  2. Fe < Mn, Ru < Tc and Os < Re
  3. Mn < Fe, Tc < Ru and Re < Os
  4. Mn < Fe, Tc < Ru and Os < Re
JEE Main 2025 (Online) 29th January Morning Shift

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