A solution of (–$$l$$) – chloro –1 – phenylethane in toluene racemises slowly in the presence of a small amount of SbCl₅, due to the formation of :

Which of the following exists as covalent crystals in the solid state?

The coagulating power of electrolytes having ions Na⁺, Al³⁺ and Ba²⁺ for arsenic sulphide sol increases in the order:

The molarity of a solution obtained by mixing 750 mL of 0.5 (M) HCl with 250 mL of 2(M) HCl will be: