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Q & A: salt water chemistry

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Most recent answer: 10/22/2007
Q:
When salt dissolves in water, why doesnít the oxygen of the water break free of the hydrogen and react with the sodium ions? P.S. What determines whether a substance is soluble in water or not?
- Keith (age 21)
USA
A:
When NaCl goes into solution it's as Na+ and Cl-. Na+ is quite stable in water, where its positive charge attracts the negative sides of polar H2O molecules. Thatís a lot different from putting metallic Na into water.

One of the main factors in determining the solubility of some molecule or ion in water is whether it either is ionic (like Na+) or at least fairly polar (with positive and negative charges somewhat separate), like many proteins. Thatís because water is highly polar. It takes a lot of energy to insert a non-polar molecule (like most oils) into water, disrupting hydrogen bonds. So non-polar molecules are usually not very soluble in water.

mike w

(published on 10/22/2007)

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