Is Magnesium Hydroxide Soluble?

Ever mixed a white powder into water and noticed it just… sits there?
That’s pretty much what happens when you try to dissolve 수산화 마그네슘.

So, is magnesium hydroxide soluble?
Let’s talk about that — in plain English — and why it matters in chemistry and real life.

What Is Magnesium Hydroxide?

수산화 마그네슘 (Mg(오)₂) is an inorganic compound made up of magnesium (Mg²⁺) and hydroxide ions (OH⁻).

It’s a white solid, slightly slippery to the touch, and commonly found in Milk of Magnesia, which is used as an antacid 그리고 laxative.

But despite being used in liquid medicines, magnesium hydroxide doesn’t actually dissolve well in water.

Understanding Solubility

Before we answer how soluble magnesium hydroxide is, let’s define what solubility means.

Solubility describes how much of a substance can dissolve in a solvent (like water) to form a homogeneous solution.

If it dissolves easily, we call it soluble (like table salt).
If only a small amount dissolves, it’s sparingly soluble or insoluble.

So where does magnesium hydroxide fit in?

Is Magnesium Hydroxide Soluble in Water?

The short answer: magnesium hydroxide is only sparingly soluble in water.

At room temperature, only about 0.0009 grams of Mg(오)₂ dissolve in 100 mL of water.
That’s less than a thousandth of a gram — practically nothing.

What happens instead?
It forms a suspension — tiny undissolved particles floating in water, giving it a cloudy or milky look.

That’s why Milk of Magnesia looks white and opaque.

The Science Behind Its Low Solubility

When magnesium hydroxide tries to dissolve, it splits into ions:

Mg(오)2⇌Mg2⁺+2OH⁻

The issue?
As soon as some OH⁻ ions form, they make the solution basic — and that high pH actually pushes the equilibrium backward, preventing more Mg(오)₂ from dissolving.

This is known as the common ion effect — a classic reason why many metal hydroxides (like Ca(오)₂ or Fe(오)₃) are poorly soluble.

Solubility and Temperature

You might expect heating the water to make magnesium hydroxide dissolve better, right?
That’s true for most solids, but not this one.

Magnesium hydroxide’s solubility actually decreases slightly with temperature — a quirk caused by the way its ions interact in water.

So even at boiling point, it’s still barely soluble.

When Magnesium Hydroxide “Seems” Soluble

Even though it doesn’t truly dissolve, magnesium hydroxide can still appear to “disappear” in certain reactions — especially in acidic environments.

예를 들어, in the stomach:

Mg(오)₂+2HCl→MgCl₂+2H₂O

Here, it reacts completely with acid to form magnesium chloride, which is soluble.
That’s why it works effectively as an antacid — neutralizing excess stomach acid.

So while Mg(오)₂ isn’t soluble in plain water, it’s highly reactive in acid, giving it major practical value.

Real-Life Example: The Cloudy Solution

When I first did this in the lab, I added a small scoop of magnesium hydroxide powder to water, stirred it hard, and waited.
It looked like milk — cloudy, no matter how long I stirred.

But when I added a few drops of acid, it suddenly cleared up!
That’s because the acid consumed the OH⁻ ions, forcing the solid to dissolve completely as magnesium chloride.

That little “magic trick” is chemistry in action — and it’s why Mg(오)₂ is both useful and safe.

Why Low Solubility Is Useful

Believe it or not, its poor solubility is a big advantage.
Here’s why:

Gentle neutralization: It reacts slowly, making it ideal for stomach acid relief.

Long-lasting effect: Because it doesn’t dissolve quickly, it releases hydroxide ions gradually.

Safe handling: It’s mild and non-corrosive, unlike highly soluble strong bases such as NaOH.

Industrial stability: It’s easy to store and handle in powders or suspensions.

Comparison: Solubility of Common Hydroxides

This shows magnesium hydroxide sits near the bottom of the solubility chart — just above aluminum hydroxide.

FAQs About “Is Magnesium Hydroxide Soluble”

1. Why is magnesium hydroxide not very soluble in water?
   Because the hydroxide ions it releases make the solution basic, preventing more from dissolving — that’s the common ion effect.
2. Is magnesium hydroxide soluble in acid?
   Yes. It reacts completely with acid to form magnesium salts like MgCl₂, which are soluble.
3. Does magnesium hydroxide dissolve better in hot water?
   Not really — its solubility slightly decreases with higher temperature.
4. What does a magnesium hydroxide solution look like?
   It’s milky or cloudy white — not truly a solution, but a suspension of undissolved particles.
5. Is magnesium hydroxide safe to drink?
   Yes, in controlled doses as an antacid or laxative(e.g., Milk of Magnesia). But always follow dosage instructions.

Final Thoughts

So, is magnesium hydroxide soluble?
No — it’s only sparingly soluble in water.

But that low solubility is what makes it so useful — gentle, stable, and safe.
Whether in medicine, water treatment, or flame retardants, its chemistry works quietly but effectively.

In short, magnesium hydroxide may not dissolve easily — but it certainly finds its place in science and industry.

Is Magnesium Hydroxide Soluble? | Simple Chemistry Explanation

Is magnesium hydroxide soluble in water?

Learn why it’s only sparingly soluble, how pH affects it, and where it reacts strongly — explained in plain English.