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You are watching: What happens when magnesium oxide is dissolved in water

Magnesium oxide is a salt, and also salts dissolve in distilled water, due to water gift polarized. As such I would mean that you would certainly find cost-free ions, i m sorry is evidenced by the water conducting electricity. But most sources I uncover states the magnesium hydroxide is created through a reaction v the water. I would certainly appreciate if someone can tell me what is correct and also why the various other one is false.

All of that is true, these facts carry out not contradict every other.

The missed component is quantification. Salts and also generally ion compounds room soluble, but solubility comes in selection of many orders of magnitude.

Also, some compounds, also if largely ionic, react with water.

So magnesium oxide reacts v water forming magnesium hydroxide, both being nearly insoluble in water.

Oxide anion together a very strong Lewis base immediatelly reacts v water $\ceO^2- + H2O -> 2 OH-$. So the just chance for steel oxides to remain being oxides is to it is in insoluble, v their lattice energy too high to be broken by water hydration of ions.

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When Melvin says that "salts dissolve in distilled water, because of water being polarized", the is by far not a general law. Part salts room soluble and some room not. Nobody is yes, really able come predict the solubility the a provided salt. There are plenty of rules describing this subject, utilizing polarity, lattice energy, or various other parameters. They are valid for plenty of compounds. But there are always strange exceptions.

A great example is the solubilities of calcium halogenides. This compounds have to have similar structures. $\ceCaCl2$, $\ceCaBr2$ and also $\ceCaI2$ space all very soluble in water, being liquified in much less that your weight that water. But $\ceCaF2$ is exceptionally insoluble in water, together it is among the most crucial minerals on planet to produce fluorine compounds. If $\ceCaF2$ was a tiny little bit soluble in water, this mineral would have actually been currently washed the end by the rains, and drained to the seas. The is no the case, together $\ceCaF2$ is a typical mineral that can be found in numerous different countries.

The basic theory for predicting the solubility of any kind of compound has actually yet to be discovered. Indigenous time to time posts are published in records like the journal of chemistry Education, because that explaining the solubility with brand-new parameters favor the electronegativity, the polarizability, the atom dimensions, the hydrogen bonds, etc. They are able to explain quite a many compounds. But there are constantly exceptions.