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How many moles of XYZ

  1. Sep 29, 2011 #1
    1. The problem statement, all variables and given/known data

    What molar concentration of each ion appear in 0.16M Pb(NO3)2?

    *Note* The title incorrectly says "moles".

    2. Relevant equations

    M = mol/L

    3. The attempt at a solution

    My teacher tells me this is wrong, but I can't see my fault:

    Molar Mass of Pb+2 = 207.20g
    Molar Mass of NO3- = 124.02g

    [itex]\frac{x}{1L} = 0.16M[/itex]

    [itex]x = 0.16mol[/itex]

    [itex]0.16mol = \frac{y*1mol}{331.22g}[/itex]

    [itex]y = 53g[/itex]

    [itex]Pb: 53g * \frac{207.20g}{331.22g} = 33g[/itex]

    [itex]\frac{33g}{331.22g} = 0.10mol[/itex]

    [itex]NO_{3}: 53g *\frac{124.02}{331.22g} = 20g[/itex]

    [itex]\frac{20g}{331.22g} = 0.06mol[/itex]

    [itex]Pb = \frac{0.10mol}{1L} = 0.10M[/itex]

    [itex]NO_{3} = \frac{0.06mol}{1L} = 0.06M[/itex]

    Any ideas where I messed up?
    Or if I did?
    Last edited: Sep 29, 2011
  2. jcsd
  3. Sep 29, 2011 #2
    I would also like to say that in my first attempt to solve this, I simply multiplied 0.16M by the fractions of mass for lead and nitrate and got the same answers.

    That was the "incorrect" version. This is my third attempt, with the same results.
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