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I read that $\ce{MgCl2}$ and $\ce{CaCl2}$ are more soluble than $\ce{NaCl}$. I think that $\ce{NaCl}$ should be more soluble due to more ionic nature. $\ce{Mg^{2+}}$ and $\ce{Ca^{2+}}$ are more polarising and have more covalent nature and thus should be less soluble. I want to know the reason why the opposite is happening.

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  • $\begingroup$ How about a few numbers? $\endgroup$ – Karl May 12 '18 at 8:18
  • $\begingroup$ Who said greater ionic character means greater solubility? $\endgroup$ – Ivan Neretin May 12 '18 at 10:53
  • $\begingroup$ there should be balance $\endgroup$ – amish dua May 12 '18 at 12:57
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I don't think there is any simple answer.There are some rules of thumb, all of which have exceptions. Most chlorides are soluble. That includes both MgCl2 and CaCl2.

Solubility is the result of the balance between competing interactions: between the ions in the salt and between those ions and the water.

Many factors contribute to the solubility of a compound in water. In this case, the main difference between the compounds is the bonds’ strength.

The longer answer is to do with something called the "enthalpy of solvation".'

you can think it this way that the lattice enthalpy in MgCl2 and CaCl2 will be less and can be easily be overpowered by hydration enthalpy

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