student32 Posted October 12, 2009 Share Posted October 12, 2009 Hi, My question is: if you were to make a solubility table, how would you make one. Im in grade 11 Chemistry. I was thinking, dissolve every element/compound into water and see if they are aqeuous. Then we can tell which metals/compounds are insoluble or soluble with each other. For Ex. Magnesium and Hydroxide, Mg(OH)2 Magnesium is insoluble with Hydroxide. How do we assume that because Hydroxide does not dissolve in water, it is insoluble with magnesium. please explain in simple terms >_< ty! Link to comment Share on other sites More sharing options...
hermanntrude Posted October 13, 2009 Share Posted October 13, 2009 there are theoretical ways to calculate the solubility of salts, but i expect these tables were made on a trial-and-error basis like you described. Your last question makes no sense... Magnesium is insoluble with Hydroxide. How do we assume that because Hydroxide does not dissolve in water, it is insoluble with magnesium. magnesium isn't ever said to be "insoluble with hydroxide". All you can really say is that magnesium hydroxide isn't soluble. I don't see why you think that we can "assume hydroxide is insoluble with magnesium because hydroxide is insoluble" no such assumption has ever been written down in a textbook. I think perhaps your problem is that you're searching for hidden meaning in the solubility rules. At this stage of learning, you can't really do anything except accept that the rules are what they are. There's no way for you to empirically derive them. Link to comment Share on other sites More sharing options...
CaptainPanic Posted October 13, 2009 Share Posted October 13, 2009 The solubility rules that I learned say that you just always have to look it up in a book. It is by far the easiest method. You have to test every salt - not every element. You can also calculate the change in Gibbs energy for the dissolution of the salt. That still includes looking up stuff (and a lot more to be honest)... and several courses in thermodynamics... But if you never heard of these words, then I'd just go with the schoolbook method of looking it up in a list and/or wikipedia. There is a theory, and logic behind the solubility of salts. But it's not to be found where you seem to be looking for it. But fear not - there are some trends which you can observe. I find that this website seems to sum them up pretty well. (And this is schoolbook material - so I don't think I am helping too much with the homework) Link to comment Share on other sites More sharing options...
hermanntrude Posted October 13, 2009 Share Posted October 13, 2009 Captain, many exams and other tests require students to memorise some "solubility rules" so that they can predict the outcomes of precipitation reactions. Your method, while better for an actual experiment, is unhelpful in these situations. Please try to remember the people who ask homework questions are not dedicated scientists who want to do things the absolute best way. Often they are hard-working students who have to learn an awful lot in a short space of time. Complicating the issue often doesn't help, even if it is more precise. Link to comment Share on other sites More sharing options...
CaptainPanic Posted October 14, 2009 Share Posted October 14, 2009 Hmm - I never had to memorize these rules. We always had a standard book (BINAS, same book for the whole country) to look up stuff like this. It contains basic info on biology, physics and chemistry. For chemistry, the solubility of some 200 salts were listed (in a matrix of positive and negative ions) and with solubility products (constants). Also, molar masses, acid-base constants, electrode potentials, dissociation constants, solubility of gases, melting and boiling points, bond lengths and angles, heat of reaction etc, etc. For physics it contains formulas, a list of the most important constants, a list of symbols used in formulas (standardized for the country, and corresponding quite well with what I found later in life), and more. I hope I'm not discouraging any students who do have to memorize stuff - but if I would have had to memorize rules like these, I probably would have failed chemistry at high school level (because I have an awful memory). But I eventually made it as far as a MSc in chemical engineering. I still look up lots of little things every day, despite the fact that I am working in chemistry for over a decade now (if you include the time I was a student). Testing the memory of students is a task best done in classes like French, Spanish or English. In real engineering life, I also have time to look things up. p.s. feel free to split this discussion off into a new thread - I know I am going off topic, and I'll even report my own post for it Link to comment Share on other sites More sharing options...
Mr Skeptic Posted October 14, 2009 Share Posted October 14, 2009 CaptainPanic, do you know of any such books that are available online? Link to comment Share on other sites More sharing options...
CaptainPanic Posted October 15, 2009 Share Posted October 15, 2009 CaptainPanic, do you know of any such books that are available online? I had a quick look, and I was surprised to find out two things about BINAS (the Dutch standard reference book): 1. BINAS is available in English 2. A sort of online "trial" version exists (scroll down, click "e-book link") with 28 out of >100 pages of BINAS is available online. No downloads or purchase needed. The free online version has page numbers, so you can see how many pages are actually left out as well. It's really just a scan of the actual book. The paper version of BINAS (English version, ISBN 978-90-01-707316) can be purchased online too... same website as I linked to before. Hope it's alright that I link to a website which is commercial. I assure everybody that I have no commercial interests in linking to it. 1 Link to comment Share on other sites More sharing options...
hermanntrude Posted October 15, 2009 Share Posted October 15, 2009 the reference book is a great thing and i agree with you that it's sensible to provide such books to students. nevertheless, this is the situation we're in. it is a disease of north america whereby people confuse knowledge and memorisation with intelligence Link to comment Share on other sites More sharing options...
Patty Raelyn Posted November 8, 2009 Share Posted November 8, 2009 How to use solubility chart to find solid liquid or gas ad if it reacts.? Link to comment Share on other sites More sharing options...
Fuzzwood Posted November 8, 2009 Share Posted November 8, 2009 Do you know what solubility means? Link to comment Share on other sites More sharing options...
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