# What is Delta H for dissolution? [closed]

An ionic compound has a solubility of $$1\ \mathrm M$$ in water at $$25\ ^\circ \mathrm C$$ and its solubility increases as the temperature is raised. What are the signs of $$\Delta H^\circ$$ and $$\Delta S^\circ$$ for the dissolving process?

Since the the solubility increases as the temperature is raised ($$\Delta G^\circ$$ becomes more negative), I know that $$\Delta S^\circ$$ is positive. However, I am unsure of how to determine the sign of $$\Delta H^\circ$$. The answer is $$\Delta H^\circ > 0$$.

## closed as off-topic by Mithoron, A.K., Jon Custer, airhuff, Mathew MahindaratneJan 21 at 9:45

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• Hint: What happens to the bonds in the substance as it dissolves... – Night Writer Jan 20 at 20:06
• I know the bonds break (delta H is positive), but I thought that some substances, like NaOH, dissolve exothermically (so delta H is negative)? – DrPepper Jan 20 at 23:38
• I am not sure the proposer of the exercise want all this but your doubt is legitimate. See here: chemistry.stackexchange.com/questions/51862/… – Alchimista Jan 21 at 10:09
• See answer about Van't Hoff equation here. – Karsten Theis Jan 21 at 15:02
• The statement about $\Delta G^\circ$ is not quite true. K becomes larger, and $\frac{\Delta G^\circ}{T}$ becomes more negative as the temperature increases. – Karsten Theis Jan 21 at 15:17