The lathanide ion that would show colour is :

The size of the iso-electronic species Cl^–,  Ar and Ca²⁺ is affected by :

In order to oxidise a mixture of one mole of each of FeC₂O₄, Fe₂(C₂O₄)₃, FeSO₄ and Fe₂(SO₄)₃ in acidic medium, the number of moles of KMnO₄ required is :

100 mL of a water sample contains 0.81 g of calcium bicrabonate and 0.73 g of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalents of CaCO₃ is : (Molar mass of calcium bicarbonate is 162 g mol^–1 and magnesium bicarbonate is 146 g mol^–1)