What Is Solubality?

[Michie]

We think of glucose first...

But maybe they're talking about SUGAR, which is sucrose

I think that's a glucose and a fructose together

[belis]

Sucrose is a sugar that is true and it is maid from flucose and fructose but it is also perfectly soluable same as glucose.

[Dobby]

Sorry, I've been ou, now let me try and answer some questions.



1.) 5a5: The substances I was given were sugar/sucrose and ethyl alchol, or at least she says that it was sugar. and the other thing is it never did say how long to stir, so how do I know that the company who composed this lab just didn't mess up?



2.) Jungle Monkey: The chart was a flow chart that told you to do one thing and then said if you got this result try this and if u got this result to try another . As you worked your way trough different mini-labs you elimated different substances or for some lucky people, identified your substance. As for do I know anything more, what else can I tell you? It was a white crystaline substance that is acidic, dissolves in water and elhyl alchl to my belief. It does not make vinigar bubble and when mixed with vinigar and then put over heat, it does not change color. (Does that help?) As for other teachers, I asked my uncle, a professor of soil sciences at Purdue University in Indiana. He has agreeded with my conclusion, however, he believes, as do I, since I did the expirement in front of her and it didn't help, any info I provide would just piss her off probably.



3.) ToraToraTora: I just looked over the papers again, and I remember doing everything the same way it says. Also, I consulted a friend who also had sucrose/sugar and they had the same results until that point, but they said they didn't stir very long...........



4:) Everyone: I think I called my substance glucose........its sucrose. I deserve that.



Thanks for all your help. I'm learning a lot.

[Dobby]

Since I had some spare time I did some more research. Sucrose ( C12 H22 O11 ) is polar, correct. (I don't have any text books to check it with anymore, school's out) Ethyl Alcohol ( CH3 CH2 OH ) is alos polar? Now unless I didn't learn anything in class this year, don't two polar substances dissolve into one another until the point of super-saturation? Then at that point a precipitant will form? Someone check this please. For peats sake if this is right, I learned this all from her and I'd like to see her go back on her words. She'd prolly find a way though.



Thx in advance

[belis]

Both are polar so sucrose is soluable in ethanol. I am just unsure why it was acidic. Should sugar be acidic? WHY? I thought they are neutaral or maybe basic due to OH groups but why acidic? Strange

[junglemonkey]

If I know my chemistry (Which I should, I've got my higher exam next week) the rule goes "like dissolves like" so yes, a polar substance will dissolve into a polar solvent. The polarity of your alcohol depends on the length of your hydrocarbon chain, and since it's only a two carbon chain (I would call that ethanol, dunno if you do to, never heard it calls ethyl alcohol before, though I see where the name is from now lol) so yes, it's definitely polar.



I would imagine the sucrose would dissolve... and eventually, depending on how much you put in, the solution, yes, would become saturated and eventually a precipitate would form. But you're much more likely to get one if it's insoluble. You'd probably need to have put quite a bit of the substance in there, I think.

[Dobby]

Belis, I can't explain why it is acidic but one expirement was to test to see if it was acidic, by adding phenotphylne. (I know the spelling is off but you get the idea) When I added the indicator to sucrose mixed with water, it did not change color indicating a base. It is an acid, but I can't explain it any further.

[junglemonkey]

If it was a base, it ain't an acid have i misunderstood lol?

[belis]

If phenolophataleine remains colorless it indicates either acid or NEUTRAL substance. Sucrose is neutral, everything correct. I don't know what kind of chemistry their are teching in USA and what level are you Dobby but it seems to me as you have some problems with standard indicators better revise that bit

[junglemonkey]

So the mystery of the acidic sucrose is solved? Never heard of that indicator. We use univeral here.

[belis]

You are using universal indicator for everything? That is impossible. Well it is in a simple experiments you perform when you are younger but not in a high school when you need to do all that acid base titrations and all that crap. Well at least that is how it works in Polish/English schools don't have experience with others.

[junglemonkey]

We use universal indicator for titrations yes. We have used stuff like Ferroxyl indicator where Iron ions are involved (I think, that was Standard Grade work so I'm a bit rusty). In the higher course I'm just finished and am sitting my final exams on we do very little practical work because it is almost all theory. The practical work we did, for the most part didn't require indicators. Stuff like making esters, reactions with oxalic acid and permanaganate ions, testing for polarity, making soaps etc. Other stuff used were the oxidising agents we tested with alcohols, hot CuO, K2CrO7, KmnO4 which I guess in a way are indicators lol.



But when we were studying acids and bases, we used pH paper and univeral indicator because it was more about strong/weak acids etc and does just fine.



I'm Scottish lol.

[belis]

I was thought that using universal indicator for titration is totaly wrong as it does not provide for a clear end point. For a titration of strong acid with strong base you should use phenoloftaleine, but I guess for school purposes when you don't need accuracy universal indicator can do. I am doing AS in chemistry and for practical examination I needed to do titration accurately to 0.01 cm3 if I use universal indicator for this I would fail exam straight away. I want to Scotland, I want to do theory. Thery is so easy. Oxidaising agents are not indicators but I see your point in here.

[Dobby]

Sorry, being stupid again, didn't mean to type base. It stayed clear meaning that the solution is either an acid or neutral. Man I just can't think and type at the same time . Also, the reason for the acid/base test was because by this time, I had narrowed it down to 5 substances 4 of which were acids. If my substance had turned pink, I could conclude I had the basic on and end the expirement there. Sadly I didn't.

[belis]

Don't be to hard on yourself Dobby, small mistake not important. Don't worry to much about that experiment. You did it wrong or maybe your teacher is wrong but does it realy metter? At least you didn't kill anybody by this mistake so there is no need to worry.

[Dobby]

Belis, let me put it this way. All year, people have tried to prove her wrong, be it on a test question or what not. Now, I have an exam lab that cost me 15 points, and I just have a strong feeling that I'm right for once. Every time someone tries to prove her wrong she either ignores them, or counter-acts its with something so out-of-our-league, that it leaves us asking more questions to the point that she gets angry with us, or it leaves us dumbfounded. I understand that while this seems small, it would be a huge step in the right direction for or class. Right now she seems invincible to us because no one can prove her wrong, but I have the chance to change that, and I'm too bull-headed to quit when I feel that I and my classmates have been wronged too many times. If we could just get her to admit her "mistake" once, maybe others would pursue their questions as I have, hopefully they wouldn't have to go to such extremes, and maybe we could have a more fair classroom setting. So, to sum it up, I guess to say I'm not doing this for myself alone, but in hopes that others will also be able to chip away at her "iron curtain" too, to make a more friendly classroom setting. Does this answer your question?

[belis]

It did. However I just wonder what are you going to argue about. If you are 100% sure that you had acid and she is claiming that it was sucrose than I see your point. But if you had sucrose (which is very possible, why not) then there is no point in arguing wit teacher. You made a mistake and that is it, reasons for this don't metter, you guesed the substance wrongly and lost marks. End of story. When I was making a mistake in qualitive analysis and than try to argue with teacher that this is not my foult as I have done all tha steps right and the chart must be wrong or sth. She always said that what she is interested in is the final answer not the reasons for this being wrong. Try to do what you thing is best for you and your class. However I tell from own experience that arguing with a teacher is a streight way ti changing your live into hel not creating a friendly clasroom environmet.

[Dobby]

OK....I understand that. Maybe I am going to far. However, what I still think is unfair about the lab is the fact that in step 11, (the dissolution) the tree diagram in the lab kit she gave us claimed that if your unknown dissolved in the Eltyl Alochol it was Boric Acid. No if's, and's or but's about it. If it didn't dissolve, you had to continue on. Since mine dissolved, I figured I was complete because that's what the paper said my substance should be if I did the lab correctly. Since, when she checked it, that was the only step I did wrongly, I just find it a little strange that even though I can scientifically prove the paper wrong, I can't get some credit for my "discovery." Maybe I need to approach this subject to her with a "how can I help you from preventing this from happening again?" Do you think that might work beter, and then just drop it from there. Maybe then I could at least feel I've accomlpished something after all this.

[belis]

I like the idea of approaching with "how can I help you from preventing this from happening again?" In fact it usualy make a good impression on a techer as this is not regarded by them as a form of attack on their competences. I myself never trust the charts completely any more (to many marks were lost becouse of this). I usualy perform some additional test to make sure my answer is right, aspecialy when jugment is maid on basis of sth as wouge as solubility. However I still wonder how the hall solubility in ethanol can be used to distinguish between substances as ethanol is unversal solvent in which both polar and non polar substances disolve (I am doing intensive reserch on this metter in my textbooks as it is realy puzzling me completely).