MgO vs BaO

(Polar molecules, Non-polar molecules, etc.)

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MgO vs BaO

Postby Meachelle_Lum_1I » Wed Nov 14, 2018 2:14 am

Hi, which molecule is more ionic/soluble in water?
MgO or BaO?
Since Mg is more electronegative than Ba, I would assume MgO is more ionic, but the textbook solutions say otherwise. (This is problem 3.79b 6th edition)

Sydney To 1D
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Re: MgO vs BaO

Postby Sydney To 1D » Wed Nov 14, 2018 9:23 am

BaO is more soluble in water than MgO because its atomic size gives the molecule a more iconic nature and less lattice energy. The MgO molecule has a cation with a smaller radius, indicating that there is strong attraction between the cation and anion in the lattice.

Summer de Vera 2C
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Re: MgO vs BaO

Postby Summer de Vera 2C » Wed Nov 14, 2018 9:24 am

Hi! I found someone who had the same question from several years ago, and I thought this person's answtper explained it pretty clearly: "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" (Irvin Xu 4I). Hope this helps!

Xiangkun Shi 3E
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Re: MgO vs BaO

Postby Xiangkun Shi 3E » Wed Nov 14, 2018 10:10 am

Since water is polar, the more polar molecule will have higher solubility. Polarity is determined by the difference in electronegativity between two atoms. Since Mg and Ba's electronegativity is 1.2 and 0.9 respectively, and O's electronegativity is 3.5, the difference between O and Ba is larger than that between O and Mg. Therefore BaO is more soluble than MgO.

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Re: MgO vs BaO

Postby Stevin1H » Thu Nov 15, 2018 12:59 am

In order to determine which molecule is more soluble in water, we would have to look at the electronegativity of both. Since Mg has an EN of 1.2 and Oxygen has an EN of 3.5, the difference in EN is 3.5-1.2 = 2.3. For BaO, the EN of Ba is 0.9 and for Oxygen it is 3.5. The difference in EN for BaO is 2.6. Since BaO has a higher electronegativity difference than MgO, it is more ionic, which makes it more soluble in water.

Max Hayama 4K
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Re: MgO vs BaO

Postby Max Hayama 4K » Thu Nov 15, 2018 10:47 am

Because Mg is smaller than Ba, it will exhibit some covalent character since the nucleus will slightly pull on the electrons around the oxygen. Therefore BaO has more ionic character than MgO.

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