Solutions and Molecular Polarity

[jessica.so]

Q: When water and chloroform, CHCl₃, are mixed, the two components separate into two distinct layers, each of which smells strongly of chloroform. Account for these observations in terms fo the polarity of the two substances involved. Describe how you could very quickly determine which of the two layers is mainly water and which is mainly chloroform.

H₂O is a polar molecule. CHCl₃ is also a polar molecule. Given that "like dissolves like" they should turn into one solution.

 

[Borek]

There is a huge difference between their polarities. And they are completely different - water 'loves' ions and molecules able of creating hydrogen bonds.

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[Blueshift5]

However, in this case, they do not.

This is because water and chloroform have different levels of polarity. Water is a highly polar molecule due to its bent molecular structure and the presence of hydrogen bonding. On the other hand, chloroform has a relatively lower polarity due to its tetrahedral molecular structure and the presence of a C-Cl bond, which is less polar than a C-O bond.

When these two substances are mixed, the polar water molecules interact with each other through hydrogen bonding, while the less polar chloroform molecules interact through weaker dipole-dipole interactions. This results in the separation of the two substances into distinct layers.

To quickly determine which layer is mainly water and which is mainly chloroform, we can use a simple physical property - density. Water has a higher density than chloroform, so the layer with a higher density will be the one that mainly consists of water. The layer with a lower density will mainly consist of chloroform. This can be confirmed by carefully layering the two liquids in a graduated cylinder and observing the distinct layers.

In conclusion, the different polarities of water and chloroform lead to their separation in a mixture. By using density as a physical property, we can easily determine the composition of the two layers in the mixture. This is just one example of how understanding the molecular polarity of substances can help us explain and predict their behavior in different environments.