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d- and f-Block Elements · Question 14

JEE Main 2026 (Online) 2nd April Evening ShiftMCQMedium📈 Topic in 13% papers+4−1
1

Among Fe2+, Fe3+, Cr2+ and Zn2+, the ion that shows positive borax bead test and with highest ionisation enthalpy is :

  1. Fe2+
  2. Zn2+
  3. Cr2+
  4. Fe3+

Answer

(4) Fe3+

Solution

Borax bead test: coloured transition metal ions give coloured metaborate beads.

Zn2+ (3d10) is colourless ⇒ negative test. Fe2+, Fe3+, Cr2+ give positive tests.

Ionisation enthalpy of the ion (removing one more electron):

Fe2+ (3d6) → Fe3+ (3d5): easy, gives half-filled d subshell

Cr2+ (3d4) → Cr3+ (3d3): easy ( Cr2+ is a reducing agent)

Fe3+ (3d5): higher charge and stable half-filled d subshell ⇒ highest ionisation enthalpy

∴ Fe3+.

Answer: (4)

JEE Main 2026 (Online) 2nd April Evening Shift

Keep practising — d- and f-Block Elements

2

Number of paramagnetic ions among the following d- and f-block metal ions is . Mn2+, Cu2+, Zn2+, Yb2+, Sc3+, La3+, Gd3+, Lu3+, Ti4+, Ce4+ (Atomic number of Mn = 25, Cu = 29, Zn = 30, Yb = 70, Sc = 21, La = 57, Gd = 64, Lu = 71, Ti = 22, Ce = 58)

JEE Main 2026 (Online) 2nd April Evening Shift
3

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 false but Statement II is true
  2. Both Statement I and Statement II are false
  3. Both Statement I and Statement II are true
  4. Statement I is true but Statement II is false
JEE Main 2026 (Online) 28th January Morning Shift
4

Consider the following statements about manganate and permanganate ions. Identify the correct statements. Choose the correct answer from the options given below :

  1. A and D Only
  2. A, B and C Only
  3. A, C and D Only
  4. A, D and E Only
JEE Main 2026 (Online) 28th January Evening Shift
5

"X" is an oxoanion of the lightest element of group 7 (in the periodic table). The metal is in +6 oxidation state in "X". The color of the potassium salt of X is

  1. purple
  2. orange
  3. yellow
  4. green
JEE Main 2026 (Online) 24th January Evening Shift
6

The oxidation state of chromium in the final product formed in the reaction between KI and acidified K2Cr2O7 solution is :

  1. +2
  2. +3
  3. +4
  4. +6
JEE Main 2026 (Online) 23rd January Evening Shift
7

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 2026 (Online) 22nd January Evening Shift
8

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
9

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
10

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
11

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

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