25 ml of a solution of barium hydroxide on titration with a 0.1 molar solution of hydrochloric acid gave a litre value of 35 ml. The molarity of barium hydroxide solution was

The number of d-electrons retained in Fe²⁺ (At no of Fe = 26) ion is :

The orbital angular momentum for an electron revolving in an orbit is given by $$\sqrt {l(l + 1)} {h \over {2\pi }}$$. This momentum for an s-electron will be given by

Which one of the following groupings represents a collection of isoelectronic species? (At. nos. : Cs : 55, Br : 35)