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In recent chemistry class , I learnt that like dissolves like I was told following points-

  1. Ionic solutes are highly soluble in polar solvents like water, ammonia etc.

Reason: The ion-dipole interactions between solvent molecules and solute's ions rip away the electrostatic forces between them and further keeps them apart, as a result the solute dissolves

  1. Covalent compounds are soluble in non-polar solvents. (no reason given for this)

So as I was told that covalent compounds are soluble in non-polar solvents, I thought of $\ce{HCl}$ soluble in water and this left me in confusion.

I think the correct statement should be polar covalent compounds dissolve in polar solvents while non-polar covalent compounds dissolve in non-polar solvents. What's correct?

Also is it possible for a polar covalent compound to dissolve in non-polar solvent(eg- $\ce{HCl}$ in $\ce{CCl4}$)?

Are the reasons written correct?

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1 Answer 1

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Pure HCl is a covalent substance, and it is a gas, that could be dissolved in covalent solvants, like toluene or carbon tetrachloride. In the presence of water, $\ce{HCl}$ immediately reacts to produce $\ce{H3O^+}$ and $\ce{Cl-}$ ions, which are soluble into water.

You should do the following reasoning. In principle, liquids should be like gases : Gases are all entirely miscible, and in any proportion. Liquids should have the same properties, and they have with non-polar molecules. But if the liquid contains hydrogen bonds between its molecule, the mixing operation requires to break these bonds. If the solute is able to recreate new bonds to replace the destroyed hydrogen bonds, Nature accepts to make a solution. This is the case with ionic compounds and polar molecules in water. If the solute is not able to make new bonds, Nature refuses to accept these foreign molecules as solute in the liquid. The mixture becomes a two-phases system.

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  • $\begingroup$ + 1,4-dioxane and diethyl ether. $\endgroup$
    – Buttonwood
    May 6, 2021 at 15:13
  • $\begingroup$ @Buttonwood What do you want to show with these two substances ? $\endgroup$
    – Maurice
    May 6, 2021 at 16:21
  • $\begingroup$ It was just an addition about HCl in solution of toluene or tetra (wait, your lab is still allowed to use it?) in these more polar organic solvents. C'est tout. $\endgroup$
    – Buttonwood
    May 6, 2021 at 17:04

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