Magnesium hydroxide has which solubility in water?

Magnesium hydroxide has which solubility in water?

• A. Soluble
• B. Insoluble
• C. Reacts with water
• D. Thermally decomposes

Answer: (B)

Magnesium hydroxide dissolves only a tiny amount in water. The solid has a very low solubility, so most of it stays undissolved and forms a suspension rather than a true solution. Only a small fraction dissociates to give Mg2+ and OH−, which is enough to make the solution slightly alkaline, but not enough to classify it as soluble. High-temperature decomposition to magnesium oxide and water isn’t about solubility in water, so it’s not relevant to this question. For these reasons, it’s described as insoluble in water.

Magnesium hydroxide dissolves only a tiny amount in water. The solid has a very low solubility, so most of it stays undissolved and forms a suspension rather than a true solution. Only a small fraction dissociates to give Mg2+ and OH−, which is enough to make the solution slightly alkaline, but not enough to classify it as soluble. High-temperature decomposition to magnesium oxide and water isn’t about solubility in water, so it’s not relevant to this question. For these reasons, it’s described as insoluble in water.