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Homework Help: Chemistry Question Solution Stochiometry And Determining The Concentration?

  1. Jan 21, 2012 #1
    1. The problem statement, all variables and given/known data

    What is the concentration of all ions after 600.0mL of 2.00 mol/L Barium nitrate is added to 100.0 mL of 2.50 mol/L sodium phosphate.

    3. The attempt at a solution
    I first wrote down the equation : 3Ba(No3)2 + 2Na3PO4 = Ba3(PO4)2 (solid) + 6NaNO3
    I then found the moles using n = c x v.
    moles of Ba(No3)2 n = 2 x 0.6L = 1.2 mols
    moles of Na3PO4 n = 2.5 x 0.1 = 0.25 mols.

    I than found the LR: 0.25 mols Na3PO4 x 3 mols Ba(NO3)2/2Na3PO4 = 0.375 mols Ba(NO3)2

    So I have more than i need for barium nitrate so my limiting reagent is sodium phosphate.

    Now what i am having trouble with is, is that should i find the excess reagent by doing 1.2 - 0.375 = 0.825 or do i have to find the mols of the solid barium phosphate and then find the limiting reagent using that.. Please help, thanks!
  2. jcsd
  3. Jan 21, 2012 #2
    anyone care to help??
  4. Jan 22, 2012 #3
    You are provided with the concentrations and volumes of the reactants. Find out the moles of reactants and the final moles of all the ions as the question says. Then divide the moles by the total volume i.e. 0.7 litres.
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