The number of statement(s) correct from the following for copper (at no. 29) is/are ____
(A) Cu (II) complexes are always paramagnetic
(B) complexes are generally colourless
(C) is easily oxidized
(D) In Fehling solution, the active reagent has
(A) Cu (II) complexes are always paramagnetic
(B) complexes are generally colourless
(C) is easily oxidized
(D) In Fehling solution, the active reagent has
Answer: 3
Solution
Analyzing each statement:
(A) Cu(II) has electronic configuration [Ar]3d⁹, with one unpaired electron, making Cu(II) complexes paramagnetic. Correct.
(B) Cu(I) has configuration [Ar]3d¹⁰ (fully filled d-orbitals), so no d-d transitions occur, making Cu(I) complexes generally colourless. Correct.
(C) Cu(I) is easily oxidized to Cu(II) because Cu(II) is more stable in aqueous solution. Correct.
(D) Fehling solution contains Cu(II) complexed with tartrate, not Cu(I). Incorrect.
Three statements (A, B, C) are correct. The answer is 3.
(A) Cu(II) has electronic configuration [Ar]3d⁹, with one unpaired electron, making Cu(II) complexes paramagnetic. Correct.
(B) Cu(I) has configuration [Ar]3d¹⁰ (fully filled d-orbitals), so no d-d transitions occur, making Cu(I) complexes generally colourless. Correct.
(C) Cu(I) is easily oxidized to Cu(II) because Cu(II) is more stable in aqueous solution. Correct.
(D) Fehling solution contains Cu(II) complexed with tartrate, not Cu(I). Incorrect.
Three statements (A, B, C) are correct. The answer is 3.
JEE Main · 2022 · 27 Jun 2022 · Shift 1 · Integer answer