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Homework Help: Writing net ionic equations (having problems!)

  1. Jan 30, 2010 #1
    We have been given three balanced equations to write as net ionic equations. Our teacher forgot to teach us this bit and has now left the college. I'm really stuck, any help would be so kindly appreciated TY x

    The equations are:

    1. Pb(NO3)2 (aq) + 2KCl (aq) = PbCl2(s) + KNO3 (aq)

    2. 2HCL(aq) + Ba(OH)2(aq) = BaCl2(aq) + 2H2O(l)

    3. NaCl(aq) + AgNO3(aq) = NaNO3(aq) +AgCl(s)

    With the first equation I dont think it is balanced, so I tried to firstly balance it by writing:

    Pb(NO3)2(aq) + 2KCL(aq) = PbCl2(s) + 2KNO3(aq)

    Then I attempted to write it ionically:

    [Pb]2+ + 2[NO3]- + [K]+ + [Cl]- = [Pb]+2 + 2[Cl]- + 2[K]+ + 2[NO3]-

    for the second one I got as far as writing: 2[H]+ + 2[Cl}- but I am very unsure of how to write Ba(OH)2. Is there 2 lots of Ba and 2 lots of OH? I don't understand why the OH is in brackets. :(

    I havent started trying to figure out the third question yet, I've spent hours trying to work out how you do the first two and I'm getting in a bit of a panic.

    If you have been so kind as to take the time to read my problem (I know it's long and I sound like a complete idiot!) then thanks so much, and if you could help me then even more thanks. xx

  2. jcsd
  3. Jan 30, 2010 #2
    Generally, whenever you see a solid, liquid, or gas in a chemical equation, that compound does not separate into ions in the net ionic equation. So in your first one, don't separate PbCl2. Then you cross out the spectator ions, or the ions that appear on both sides of the equation, and what you have left makes the net ionic equation.

    For Ba(OH)2 in 2, think about the charges of the ions: Ba2+ and OH-. You need two OH- ions to balance the charge of Ba2+.
    Subscripts after parentheses apply only to what is inside the parentheses.
  4. Jan 31, 2010 #3
    Thanks so much Bohrok, it's starting to make sense (I think!)...for the first one I have got:

    Pb2+ + 2Cl- = PbCl2

    and for the second:

    2H+ + 2OH- = 2H2O

    and for the third:

    Cl- + Ag+ = AgCl

    am I correct? x
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