AS Level Chemistry 2025 – 400 Free Practice Questions to Pass the Exam

Sodium hydroxide (NaOH) is a classic example of a soluble base. It is highly soluble in water, which means that it readily dissociates into sodium ions (Na⁺) and hydroxide ions (OH⁻) when dissolved. This property allows it to effectively increase the pH of a solution, making it a strong base commonly used in various applications, such as in laboratories and for industrial processes.

The solubility of NaOH is attributed to its ionic nature, which allows it to interact successfully with water molecules, thus facilitating the ionization process. This high solubility contrasts with other hydroxides like calcium hydroxide (Ca(OH)₂) and magnesium hydroxide (Mg(OH)₂), which are only slightly soluble in water, meaning they do not produce as many hydroxide ions upon dissolution. Barium hydroxide (Ba(OH)₂) is more soluble than calcium and magnesium hydroxides, but it is still not as soluble as sodium hydroxide.

Therefore, when identifying a soluble base, sodium hydroxide stands out due to its significant solubility in water, leading to its widespread use as a strong base in various chemical reactions.