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Topic: Sugar dissociation in water  (Read 166 times)

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Offline iOSM

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Sugar dissociation in water
« on: November 16, 2020, 03:53:54 PM »
Greetings dears,

I have been looking for an answer regarding the water final temperature and by how much it will be reduced when sugar is being dissolve.

I was thinking that since sucrose is a polar covalent compound unlike salt it may not need much of energy from the hot water to break apart the sugar molecules but i’m not quite sure about this if it is correct or not (assuming no stirring is performed)

Therefore i’m assuming that the temperature change is insignificant if we for example dissolve 4 grams of sugar in 200ml of water.

i have obtained enthalpy of formation for sucrose in water which is equal to 6kJ/mole and calculate the final temperature which results in very low temperature decrease. I thought of it as a reasonable answer because the freezing point depression and melting points rise for solution are not that much significant when dissolving covalent compounds

https://pubs.acs.org/doi/10.1021/ja01164a504

i appreciate your input
thnx

Offline Borek

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Re: Sugar dissociation in water
« Reply #1 on: November 16, 2020, 04:35:10 PM »
It can be partially a language problem, but I have a feeling you are throwing into the problem everything you've heard about, regardless of whether it matters or not.

There is no dissociation, "enthalpy of formation of sucrose in water" doesn't sound OK (I suppose you mean heat of solution), freezing point depression and boiling (not melting) point rise are a separate thing.

Yes, the paper you linked to suggests heat of solution of around 6 kJ/mol, and yes, the temperature change during dissolution is below accuracy of most lab thermometers. Whether it is negligible depends on your application.
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