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Postby HimaniMadnawat3L » Tue Oct 28, 2014 7:43 pm

In the homework, 2.77 asks: Use electronegativities to predict which of the following compounds is the more soluble in water: (a) AlCl3 or KCl; (b) MgO or BaO.

I understood the answer for part (a) since Al3+ is smaller and more highly charge and causes stronger polarizing power on the anion. For part (b), I thought that the Mg2+ cation would have a higher polarizing power than Ba2+, thus making MgO more soluble in water, but the answer key says it's BaO. Any help?

Irvin Xu 4I
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Re: 2.77

Postby Irvin Xu 4I » Wed Oct 29, 2014 5:17 pm

For part a, I actually think that KCl would be more soluble in water, because like dissolves like, meaning polar solutes dissolve well in polar solvents. Since KCl is more ionic (greater difference in electronegativity) it will dissolve better in water than AlCl3 will. As for part b, Ba has a lower electronegativity than Mg does, so the difference in electronegativity would be greater for BaO, meaning it is more ionic, and thus, more polar. Therefore, BaO should be more soluble in water.
Hope this helps.

Justin Le 2I
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Re: 2.77

Postby Justin Le 2I » Wed Nov 05, 2014 11:54 am

The answer key says that KCl is the more soluble of the two choices in 2.77a.

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