Organic liquids A, B, and C have densities of 0.690, 0.955 and 1.126 g/mL, respectively. A and C are low polarity solvents, while B is a highly polar solvent. If each were added to water separately, how would you expect them to behave? (address solubility and density)
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The first thing to do is determine the polarity and density of water. The density of water is 1.00 g/mL. Because the electronegativities of hydrogen and oxygen are not close at all (2.2 for hydrogen and 3.44 for oxygen), water is definitely polar. With this information, we can compare it with the given information to determine what will happen.
Adding Solvent A to Water:
Solvent A is lowly-polar and less-dense than water. Because solvent A is less-dense, it will float on or just below the surface of the water. Because 'like dissolves like', solvent will not dissociate in water a large amount.
Adding Solvent B to Water:
Solvent B is very polar and about the same density of water. Because the densities are very similar, you would expect solvent B to be distributed evenly throughout solution. Going back to 'like dissolves like', because solvent B is very polar, you can expect to dissociate very well in water.
Adding Solvent C to Water:
Solvent C is lowly-polar and more-dense than water. Because solvent C is more-dense than water, it will sink to the bottom. Solvent C behaves similar to solvent A in terms of dissociation because they have the same polarities.
Just a note: the question mentioned solvents A and C have low polarities. When put in water, they will dissociate a little, but in general won't do much.
'Like Dissolves Like'
The phrase 'like dissolves like' is a common term in solubility chemistry to explain that molecules of the same polarities will dissolve each other. Polar molecules will generally dissolve other polar molecules, while non-polar will dissolve non-polar. (That's a really simplified explanation of solubility; it can get complicated.)