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Homework Help: Urgent help needed with Moles question

  1. Jan 6, 2013 #1
    A group of students decided to use AAS to analyze three different brands of iron tablets to determine their content. They placed a tablet in a 100 mL beaker with 6 mol/L HCl and covered it with a watch glass and heated slowly for 15 min. They then filtered the solution into a 250 mL volumetric flask and topped it up to mark with distilled water.

    They determined the absorbance of the sample and repeated the same process for the other two samples

    Sample A: Absrobance =0.85 concentration of iron in solution = 4.7 ppm
    Sample B Absorbance = 0.8 Concentration of iron in solution = 0.6 ppm

    Calculate the concentration of iron in the tablet itself.

    2. Relevant equations

    Molarity = n/v

    3. The attempt at a solution
    I have no clue what to do. If only somebody can point me in the right direction I would be very grateful.
  2. jcsd
  3. Jan 6, 2013 #2


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    Homework Helper
    Education Advisor
    Gold Member

    Obviously sample A and sample B are either of different brands or of different product editions. Helpful fact to know is that parts per million (abbreviated, "ppm") is nearly the same as milligrams per liter. You already know that the solutions prepared for each sample are 250 ml. each. You need to know the atomic weight of iron, which you can find in common reference works such as Periodic Table. You are interested in amount of iron in each tablet.

    n/v ....... How many moles of iron in how much volume of solution? Each 250 ml. solution contains the iron from the tablet sample.
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