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I am curious about the effect that adding potassium chloride to water in varying concentrations has on its specific heat capacity. I have been unable to find any online information about this? Theoretically, would one expect a linear relationship or something different? Furthermore, how would this change if we added another soluble material to water? Any insights on the same would be much appreciated.

Note: This question has been previously asked here but received no responses even with a bounty. Hence, I am posting it here.

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  • $\begingroup$ How exactly I have been unable to find any online information about this looks like? Explicit effort evidence is required, even if no usable info was found. $\endgroup$
    – Poutnik
    Feb 23, 2022 at 10:51

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Generally, solutions are not like a mixture of peas and beans, where the specific heat capacity would be a linear combination of the ones of pure peas/beans.

The relationship is generally nonlinear. Solutes and solvents form bonds and structures not present in pure substances, having different participation in heat capacity. OTOH, the lattice stractures of the solid disappear. All that is furthermore concentration dependent.

For $\ce{KCl}$ and water, there is various degree of $\ce{K+}$ and $\ce{Cl-}$ hydration, affecting the specific heat capacity value. As $\ce{H2O}$ molecules bound to each other by hydrogen bonds have different effective degrees of freedom than if they are partially bound to ions.

This can be approximated by linear relationship, but deviations of that have to be evaluated experimentally, unless there is already empirical handy data for that, in form of a table or empirical formula. As water has, AFAIK, the highest specific heat capacity of all condensed matter, the specific heat capacity would generally decrease with concentration.

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