Polarity and solubility of AgCl

[Abu]

Hi everyone. I am a beginner in chemistry (introductory) so my knowledge is pretty limited when it comes to this subject.

From what I have been taught, like dissolves like, meaning polar dissolves polar and non-polar dissolves non-polar. The electronegativity difference of AgCl is around 1.3, which makes it polar covalent (which is strange because I thought AgCl was an ionic bond since it is a metal and nonmetal). In water, AgCl is insoluble - but how come? The electronegativity difference of H2O is 1.5, which also makes it polar covalent. So shouldn't the water dissolve the AgCl? Is this an exception? When I tried researching this question, some people even said that AgCl is non-polar covalent, which seems incorrect to me.

Another example is AgCl in potassium nitrate. Potassium nitrate is an ionic bond because it consists of a cation and anion, AgCl is a polar covalent bond due to the EN difference, despite being ionic in the sense that it is metal and nonmetal. Since one is Ionic and the other is polar covalent, it makes sense to me why AgCl does not dissolve in potassium nitrate, and should instead form a precipitate.

So how come AgCl will not dissolve in water, where it seems that the rule like dissolves like should apply?

 

[Martin0001]

Being polar, ionic or covalent has little to do with solubility.
So for example BaSO4 is certainly ionic and very poorly soluble. You may call it "insoluble" if you wish.
MgSO4 is ionic and very well soluble.
Hg (CN)2 is covalent and well soluble
CBr4 is covalent and insoluble
HCN is polar and soluble
PbO2 is polar and insoluble

AgCl is not an exception.
Other poorly soluble chlorides are for example PbCl2, TlCl, CuCl

 

[Abu]

Being polar, ionic or covalent has little to do with solubility.
So for example BaSO4 is certainly ionic and very poorly soluble. You may call it "insoluble" if you wish.
MgSO4 is ionic and very well soluble.
Hg (CN)2 is covalent and well soluble
CBr4 is covalent and insoluble
HCN is polar and soluble
PbO2 is polar and insoluble

AgCl is not an exception.
Other poorly soluble chlorides are for example PbCl2, TlCl, CuCl

Hi martin. Thanks for your time and response. Regarding your reply, isn't solubility relative? When the term 'well soluble' and 'insoluble' are used, aren't they are referring to their solubility in a particular solvent? A compound may be insoluble in one substance, but greatly soluble in another. Are your examples referring to solubility in water?

Also - how come polarity has little to do with solubility? I searched up the rule of like dissolves like (with regards to polarity) and it seems to have many applications. Since you are implying that there are exceptions to this rule, what are the exceptions based on? Is it bond strength?

Thanks!

 

[Martin0001]

Hi martin. Thanks for your time and response. Regarding your reply, isn't solubility relative? When the term 'well soluble' and 'insoluble' are used, aren't they are referring to their solubility in a particular solvent? A compound may be insoluble in one substance, but greatly soluble in another. Are your examples referring to solubility in water?

Also - how come polarity has little to do with solubility? I searched up the rule of like dissolves like (with regards to polarity) and it seems to have many applications. Since you are implying that there are exceptions to this rule, what are the exceptions based on? Is it bond strength?

Thanks!

In my first post I was specifically discussing solubility in water.
General rule is that alike likes alike, Eg polar is soluble in polar, covalent in covalent and ionic in ionic. Polar compounds seem optimal because they are between and have a good chance to dissole widest range of substances.
However there are so many exceptions that atempts to make watertight general rules are failing. If in doubt find me a solvent for diamond or red phosphorus (both are covalent).
There is much more to solubility than that.
Silver chloride is for example reasonably soluble in pyridine (about 50g/L at 0*C and 20g/L at 20*C). Pyridine has formua C5H5N.

My off hand definition:
well soluble - more than 100g/L
soluble 10-100g/L
poorly soluble is anything of solubility greater than gypsum (about 2g/L) but less than 10g/L
"Insoluble" is anything below that but really insoluble compounds are rare (eg HgS). 1 gram of HgS would be dissolved at equilibrium in 100000L means 100m3 of water.
These are just off hand definitions, science has nothing to say about interpretation of common language.

 

[Tom.G]

If in doubt find me a solvent for diamond...

Hot Steel. (If you believe Wikipedia: https://en.wikipedia.org/wiki/Material_properties_of_diamond)

 

[adianadiadi]

Solubility requires breaking of old bonds and making of new attractions with the solvent. If the old bonds are stronger than the new attractions with solvent, then that will be sparingly soluble.

 

[Martin0001]

Hot Steel. (If you believe Wikipedia: https://en.wikipedia.org/wiki/Material_properties_of_diamond)

there is a chemical reaction involved.
Cementite (iron carbide of composition Fe3C) is formed. This one often decomposes during cooling and graphite is separated.

 

[Martin0001]

Solubility requires breaking of old bonds and making of new attractions with the solvent. If the old bonds are stronger than the new attractions with solvent, then that will be sparingly soluble.

Yes. it is grossly right.