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Homework Help: Calculating the molarity of ions

  1. Sep 24, 2010 #1
    1. The problem statement, all variables and given/known data
    When a reaction mixture with a total volume of 4 L that contains 9.99 g of solid CaSO4 was stoichiometrically produced as per the balanced equation with 2.50 L of aqueous Ca2+, what molarity (M) of Ca2+ was required?

    Al2(SO4)3(aq) + 3 CaBr2(aq) → 2 AlBr3(aq) + 3 CaSO4(s)

    2. Relevant equations
    Stoichiometric ratios.

    3. The attempt at a solution
    Conversion of CaSO4 to mols = 1.36 mols
    molar mass = 340.0 mol/L
    After this, I don't know how to find the molarity of the Ca2+ ions...
  2. jcsd
  3. Sep 25, 2010 #2


    User Avatar

    Staff: Mentor

    Not sure if I understand what you are asking. I assume you mean you need to know what was molarity of Ca2+ solution if mass of precipitated calcium sulfate was 9.99g.

    First - 9.99g is not 1.36 mole.

    Second - concentration is moles/volume.

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