For the following Assertion and Reason, the correct option is

Assertion (A): When Cu (II) and sulphide ions are mixed, they react together extremely quickly to give a solid.

Reason (R): The equilibrium constant of
Cu²⁺(aq) + S^2–(aq) ⇌ CuS(s) is high because the solubility product is low.

Which of the following compunds will show retention in configuration on nucleophilic substitution by OH^– ion?

Consider that a d⁶ metal ion (M²⁺) forms a complex with aqua ligands, and the spin only magnetic moment of the complex is 4.90 BM. The geometry and the crystal field stabilization energy of the complex is

For octahedral Mn(II) and tetrahedral Ni(II) complexes, consider the following statements:

(I) both the complexes can be high spin.
(II) Ni(II) complex can very rarely be low spin.
(III) with strong field ligands, Mn(II) complexes can be low spin.
(IV)aqueous solution of Mn(II) ions is yellow in colour.

The correct statements are :