MediumChemistryHigh School (11–12)SolutionsConceptual

A student pours 100 mL of acetone into 100 mL of chloroform in a flask…

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A student pours $100\ \text{mL}$ of acetone into $100\ \text{mL}$ of chloroform in a flask. The flask feels warm, and the volume of the mixture is a little less than $200\ \text{mL}$ . (a) Is the solution ideal? (b) Give the signs of $\Delta_{mix}H$ and $\Delta_{mix}V$ . (c) Say what kind of deviation the pair shows and explain it in terms of molecules.

Need a reminder? The key ideaShow

An ideal solution obeys Raoult's law at every composition, with $\Delta_{mix}H = 0$ and $\Delta_{mix}V = 0$ . A positive deviation has a pressure above the Raoult line, a weaker A–B attraction, $\Delta_{mix}H > 0$ and $\Delta_{mix}V > 0$ . A negative deviation is the opposite. The deviation is $\dfrac{P_{measured} - P_{Raoult}}{P_{Raoult}} \times 100\ \%$ .

The worked solution

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