Prolonged heating is avoided during the preparation of ferrous ammonium sulphate to :

Which of the following statements are correct?

(A) The M$$^{3+}$$/M$$^{2+}$$ reduction potential for iron is greater than manganese.

(B) The higher oxidation states of first row d-block elements get stabilized by oxide ion.

(C) Aqueous solution of Cr$$^{2+}$$ can liberate hydrogen from dilute acid.

(D) Magnetic moment of V$$^{2+}$$ is observed between 4.4 - 5.2 BM.

Choose the correct answer from the options given below :

The octahedral diamagnetic low spin complex among the following is :

Using column chromatography, mixture of two compounds 'A' and 'B' was separated. 'A' eluted first, this indicates 'B' has