Which of the following in incorrect for the hydroxides of alkali metals ?

Options

A. They are white crystalline solids.
B. These caustic alkalies are the strongest bases known in aqueous solution.
C. They readily dissolve in water with the evolution much heat. The solubility in water decreases as move down the group.
D. The basis strength of hydroxides increases on moveing down the group.

Answer

C

Explanation

As we move down the group, the solubility of the hydroxides increases because the decrease of lattice energy is more than the decrease of lattice energy is more than the decrease of hydration energy. The hydroxides of Na, K, Rb, and Cs are very soluble in water (more than 100 g per 100 g `H_(2)O " at " 25^(@)C`), but LiOH is much less soluble `(13.0 g//100 g H_(2)O " at " 25^(@)C)`. The evolution of much heat is on account of intense hydration.
As we move down the group, the ability of M to release electrons towards O in `M to OH` increases due to the increase of electropositive character. As a result, the M-O bond in MOH can easily break giving `M^(+) "and" OH^(-)` ions.