Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Forming precipitates

  1. Apr 14, 2008 #1
    1. The problem statement, all variables and given/known data
    I have H2SO4 + BaCl2 → and need to figure out what it will create.

    2. Relevant equations
    Now I don't know how to figure out ionic charges or the rules of writing ions/chemical equations. I mean tried to break that up in class today into separate ions and my teacher said you can't have h2 all by itself... why is that?

    3. The attempt at a solution
    I'm at this so far:
    2H + SO4 + Ba + Cl2 →
    H2 + SO4 + Ba + Cl2 →

    How do I know how to write certain things, for instance my teacher also said you cant write 20, it needs to be o2 why is this? Also how do I determine ionic charges of things?
  2. jcsd
  3. Apr 14, 2008 #2
    What is the charge on the SO4 diatomic ion? What combines with SO4 to turn it into an insoluble compound?

    From what I'm reading here, this looks like a problem designed to test your knowledge of the solubility rules. As is the case with many solubility rules problems, this one looks like it is also testing you on your knowledge of ionic charges -- this is just something you need to know how to do, and sometimes the only way of knowing the charge of something (such as the diatomic ions) is through memorization.
  4. Apr 14, 2008 #3
    and those rules are?
  5. Apr 15, 2008 #4
    Here's ahttp://www.csudh.edu/oliver/chemdata/solrules.htm" [Broken], but they really should be in your text book.
    Last edited by a moderator: May 3, 2017
  6. Apr 15, 2008 #5
    this is chemistry that you learn in lower classes! have you just got into high school?!
  7. Apr 15, 2008 #6
    If he's in high school chemistry, then these would be the types of problems that he'd work. Is there something wrong with that?
  8. Apr 15, 2008 #7
    awww i'm sorry.... i didn't mean it like that....
    sry again
  9. Apr 15, 2008 #8
    aww god so still noooo help :((( and yes im in HS
  10. Apr 15, 2008 #9
    Part of your problem is that you are writing molecules rather than ions for the ionic equation. Try this:

    2H^+1 + SO4^-2 + Ba^+2 + 2Cl^-1

    Then use the solubility rules mentioned above and find out which ions form precipitates and which remain in solution after the reaction is complete. If you need any more help, just let me know.

    (I could repost the equation with LaTeX if this is kind of unreadable--just let me know.)
  11. Apr 16, 2008 #10
    solubility rules you have to learn:

    all nitrates (NO3-) are soluble
    all chlorides (Cl-) are soluble except lead chloride (PbCl2) and silver chloride (AgCl2)
    all sulphates ((SO4)2-)are soluble except lead sulphate (PbSO4), barium sulphate (BaSO4) and Calcium sulphate (CaSO4) which is sparingly soluble.
    all alkali metal salts are soluble (sodium (Na+), potassium (K+),.... salts)
    all ammonium (NH4+) salts are soluble
    all carbonates ((CO3)2-) are INSOLUBLE except alkali metal carbonates (sodium carbonate Na2CO3,....) and ammonium carbonate ((NH4)2CO3)

    this is what you need in HS ;)
  12. Apr 16, 2008 #11
    when dealing with ionic compounds you have to satisfy the charge. an ionic salt will consist of a positively charged ion (cation) combined with a negatively charged ion (anion). the magnitude of the charges of both ions should be equal.

    for example, with magnesium sulphate. magnesium ion is Mg2+ and sulphate ion is (SO4)2-
    the salt is then MgSO4 since the magnitude of charges on both ion is 2.

    but with sodium sulphate, sodium ion is Na+ and the sulphate ion is (SO4)2-
    the salt is then Na2SO4. there are 2 sodium ions so that in total the positive charge is +2. this balances with the -2 charge on the sulphate.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook