Why are hydroxides of earth alkaline metals are so insoluble in water?

So, in summary, the hydroxides of Earth alkaline metals are insoluble in water because of their strong ionic bonding and polar nature, which allows them to do hydrogen bonds and permanent dipole interactions with water molecules. Even smaller compounds like Mg(OH)2 have very low solubility due to these factors.
  • #1
jaumzaum
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Why are hydroxides of Earth alkaline metals so insoluble in water?
They are polar compounds and have an OH group, so they should do hydrogen bounds with water, as well as permanent dipole interactions, which in my conception are strong forces.
Even Mg(OH)2, witch do not have a big mass, has a solubility of just 1,4 mg/100ml
Can anyone help me to understand this?
 
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  • #2
jaumzaum said:
They are polar compounds and have an OH group, so they should do hydrogen bounds with water, as well as permanent dipole interactions, which in my conception are strong forces.

Yes, but the ionic bonding between a alkaline oxide metal with two positive charges and a hydroxyl ion are even stronger (more than twice as strong as in a corresponding alkali metal given that the ionic radii are smaller, too).
 

Related to Why are hydroxides of earth alkaline metals are so insoluble in water?

1. Why are hydroxides of earth alkaline metals insoluble in water?

The insolubility of hydroxides of earth alkaline metals in water is due to their high lattice energy. This means that the bonds holding the ions together in the crystal lattice are very strong, making it difficult for water molecules to break them apart and dissolve the hydroxides.

2. Which earth alkaline metal hydroxides are the most insoluble in water?

All hydroxides of earth alkaline metals are relatively insoluble in water, but the most insoluble ones are beryllium hydroxide (Be(OH)2) and magnesium hydroxide (Mg(OH)2). This is because they have smaller ionic radii and higher lattice energies compared to the hydroxides of other earth alkaline metals.

3. Why do hydroxides of earth alkaline metals form basic solutions in water?

When hydroxides of earth alkaline metals are added to water, they undergo hydrolysis, meaning they react with water molecules to form hydroxide ions (OH-) and cations of the metal. These hydroxide ions make the solution basic, giving it a pH greater than 7.

4. Can hydroxides of earth alkaline metals ever dissolve in water?

While hydroxides of earth alkaline metals are generally considered insoluble in water, they can dissolve slightly in very acidic or basic solutions. This is because the presence of excess H+ or OH- ions can disrupt the crystal lattice and allow for some hydroxide ions to be released into the solution.

5. What are some practical applications of the insolubility of hydroxides of earth alkaline metals in water?

The insolubility of these hydroxides makes them useful in various industrial processes, such as water treatment, where they can be used to neutralize acidic water. They are also used in the production of ceramics, where they help to improve the strength and durability of the final product.

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