Arrange the following bases in increasing order of their basic strength: 1. Sodium hydroxide 2. Magnesium hydroxide 3. Aluminium hydroxide 4. Ammonium hydroxide Select the CORRECT answer using the Code glVen below: Codes :

The basic strength of hydroxides depends on the ease with which they release hydroxide (OH-) ions in water [1]. Sodium hydroxide (NaOH) is a strong alkali that dissociates completely, making it the strongest base in the list. Magnesium hydroxide (Mg(OH)2) is a moderately strong base, while Aluminium hydroxide (Al(OH)3) is amphoteric and significantly weaker. Ammonium hydroxide (NH4OH) is a weak base because it only partially ionizes in aqueous solution. Following the periodic trend, basicity decreases as the metallic character decreases and the charge density of the cation increases (Na+ < Mg2+ < Al3+). Higher charge density leads to stronger covalent character in the M-OH bond, reducing basicity. Therefore, the increasing order of basic strength is Ammonium hydroxide (4) < Aluminium hydroxide (3) < Magnesium hydroxide (2) < Sodium hydroxide (1).

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Mg(OH)2 (s) → H O2 Mg2+(aq)+2OH– (aq) > p. 24