On Nov 12, 4:54*pm, "Ray B" wrote:
It depends upon whether it is an ionically-bonded compound or not, doesn't
it?

That's the general rule that we were taught in General Chemistry ISTR.
But, if memory serves,
covalently bonded chemicals tend to be insoluble unless they have an
uneven charge distribution
spatially. Alcohols are an interesting group that dissolves but
doesn't dissociate due to the
hydroxyl group that introduces a spatial charge disparity.

My previous example of sucrose is an interesting exception to that
rule because they will
dissociate upon heating. Brewers use the fact that sucrose hydrolyzes
to produce an invert
sugar that has better fermentation properties (though an acid is
usually employed as a
catalyst). Cooks also "invert" sucrose by an addition of corn syrup
(aka fructose) while
heating a sucrose solution to prevent crystalization during cooling.

Dave


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"dbs" wrote in message

...
On Nov 9, 6:09 am, "Ray B" wrote:

Duncan,

Once a compounds dissolve, they do dissociate, so I am uncertain of the
point of your comment about them.

Umm, that's not quite true is it? For example, sugar (e.g. sucrose)
dissolves but doesn't dissociate. Sucrose will hydrolize but that's a
separate reaction from dissolution and requires a catalyst/enzyme or
heating for any significant hydrolysis to take place. Although in the
vast majority of cases compounds do dissociate when they dissolve the
point is that it is not true that dissolution = dissociation. While
not very relevant to the discussion his point is valid.

Dave