Question

You cleaned your glassware prior to beginning but didn't ensure that it was completely dry and contaminated your reaction with Acetone. What effect would this have on the reaction? Draw any possible byproducts that may result from this contamination.

Answer 1

When acetone is completely dissolved in water, any sample of the solution delivers equal parts acetone and water. Sometimes, dissolving acetone in water creates the appearance of bubbles. The bubbles are likely not an indication of the chemical reaction. Bubbles may be introduced through air that is trapped in the solution when acetone is poured into the water. Some solutions bubble because the chemical reaction between ingredients generates enough heat to boil; this is not the case with acetone and water.

acetone is polar and water is polar. the solubility rule is as follows: "like dissolve like" meaning the more similar the polarity of two substances, the greater their ability to interact with each other. so since water is polar and acetone is considered polar then they there soluable.

There is no chemical reaction occurring when acetone and water mix; being polar, the acetone simply dissolves in water.

There are two immediately possible causes of the bubbles you saw;

1) When you pour one liquid in to another, the liquid being poured entrains some of the air it falls to in to the receiving liquid - so, for example, as you pour acetone in to water, the turbulence of the falling acetone, and of the "splash" when it hits the liquid surface, drags some air below the surface of the water. As the solution stabilizes, the buoyant air will rise to the surface - in the case of gentle pouring, this is very likely to be in the form of small pockets of air, making small bubbles. Similarly, stirring a mixture to make sure it's mixed can entrain air.

2) Whenever a substance dissolves in a solvent, there is a temperature change associated with the change in molecular structure. So, for example, when sulfuric acid is dissolved in water, the resulting heat is enough to boil the solution. In other cases, there can be a drop in temperature, as happens when salt (sodium chloride) is dissolved in water.

There is no way of knowing beforehand whether a solvent - solute mix will get hotter or colder when mixing happens, you have to do an experiment. The following paper, on acetone-water properties, suggests that when acetone and water are mixed, they give off heat: http://www.springerlink.com/content/1641302271221p13/ . If this is the case, then the solution they form will be quite warm, warmer than the starting liquids. You may remember that a liquid can dissolve more gas at lower temperatures, and that as the temperature rises, dissolved gases tend to bubble out of solution. It is possible, then, that dissolving acetone in water generates enough heat to force some of the air naturally dissolved in the water out of solution, again forming bubbles. I have yet to verify the report in the above paper by doing an experiment myself, so I offer it only as a useful possibility.

Hope that helps, and if you have any further questions, just send a follow-up.