Lab Report Alcohol Solubility in Water

[Colin]

So I'm designing a lab and i'm trying to test the solubility differences between methanol, ethanol, propanol, and butanol. My current experiment is taking 100 ml of water and pouring it into the reaction vessel. I then take 2 ml of the alcohol and pour 2 drops of blue food coloring into it. I then put the reaction vessel with water on a hot plate (with heat OFF, JUST USED FOR STIRRING). I then pour the alcohol into the water and set the stir to a low setting. The only problem I have is that when i test the experiment, the more carbon atoms there are, the faster the food coloring disperses (to the bottom). Shouldn't it be the opposite way around as in the mixtures with the fewest carbons dissolve fastest? Somebody help me please and tell me what's going wrong or if i'm doing it right. I'm using food coloring to see when the alcohol is dissolved, since water and alcohols are both colorless. Is there another way to test the solubilities of these liquids and find their differences?

[genepeer]

Maybe it's a temperature irregularity.

Edited November 18, 2010 by Gene-Peer

[Drake Glau]

Are you sure it's not just the food coloring dispersing to the bottom? I don't know how exactly alcohol and food coloring mix and if they stay together but it could be possible for them to separate maybe and so the food coloring is dispersing and leaving the alcohol behind. And how much "faster" is it dispersing?

[unoit5329]

I would agree with Drake. I wouldn't think there is a physical or chemical bond between food coloring to alcohol. Also there is definitely no reaction. Unless you know this for a fact, don't assume it, and therefore this is a flawed experiment.

Assuming the alcohol and food coloring did remain together and neither mixed with the water, then yes the smallest carbon chains would dissolve fastest. Having said that, I don't think that there is a noticeable difference between the time it takes for small carbon chains to dissolve. As a general rule, small carbon chains are soluble in water and large ones are not.

Lastly (still assuming the above), I wouldn't think that the food coloring dispersing to the bottom is a measure of solubility. It is a better measure of density, which tells you nothing in this case. The alcohol is also less dense than water and would float.

Hope I helped. Let me know if I didn't.

[Drake Glau]

I would agree with Drake. I wouldn't think there is a physical or chemical bond between food coloring to alcohol. Also there is definitely no reaction. Unless you know this for a fact, don't assume it, and therefore this is a flawed experiment.

Assuming the alcohol and food coloring did remain together and neither mixed with the water, then yes the smallest carbon chains would dissolve fastest. Having said that, I don't think that there is a noticeable difference between the time it takes for small carbon chains to dissolve. As a general rule, small carbon chains are soluble in water and large ones are not.

Lastly (still assuming the above), I wouldn't think that the food coloring dispersing to the bottom is a measure of solubility. It is a better measure of density, which tells you nothing in this case. The alcohol is also less dense than water and would float.

Hope I helped. Let me know if I didn't.

Just to clarify (assuming I understand what he's doing), since he is testing the solubility of alcohol in water if the food coloring does stick with the alcohol and then you see the blue disperse that would mean that the alcohol (and the blue with it) dissolved in the water.

On another note, how did you plan on measuring this? You need quantitative and qualitative data and I can't figure out a way to test for solubility honestly since measuring the amount of alcohol in the solution would be the same unless the water and alcohol formed a new compound that isnt alcohol...

[Colin]

quantitative would be the time (stop watch) until the blue reached the bottom and qualitative would be same for all being that the blue color dspersed through the solution starting off as a cloud and then becoming one giant layer

[Drake Glau]

quantitative would be the time (stop watch) until the blue reached the bottom and qualitative would be same for all being that the blue color dspersed through the solution starting off as a cloud and then becoming one giant layer

I don't think time is going to help you conclude the solubility of alcohol? Unless you find its rate of dispersion maybe? o.O

[genepeer]

Maybe, the longer chains "disperse to the bottom" (i.e. sink) because they're heavier. Solubility refers to the maximum amount of a solute that can be dissolved in a solvent. You seem to be investigating how fast a solute will fall to the bottom of a solution.

Try this: You have 100ml of water in a conical flask, keep adding the alcohol through a burette and stirring until a (oily) film starts forming at the bottom or top (depending on the density of the alcohol) of the solution. At this point, the solution is saturated and you know the amount of alcohol needed to saturate 100ml of water. This could be it's solubility.

edit: I don't think food coloring will help in the investigation since it's also a solute.

Edited November 20, 2010 by Gene-Peer