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Homework Help: Density question

  1. Sep 12, 2012 #1
    1. The problem statement, all variables and given/known data

    The density of a solution of ferric chloride is 1.058g/cc, and it is 7.00 percent by mass. What volume of the soltion (in mL) do you need to supply 34.0g of ferric chloride?

    2. Relevant equations


    3. The attempt at a solution

    Not sure where to begin. I dont understand the statement, " and it is 7 percent by mass". Does this mean i ned to multiply 34*0.07? then just calculate the volume by rearranging the density formula?
  2. jcsd
  3. Sep 12, 2012 #2
    It means that 100 g of the solution contains 7 g of ferric chloride.
  4. Sep 12, 2012 #3
    Where do I even begin on this question?
  5. Sep 12, 2012 #4
    You know the absolute mass of ferric chloride you need to supply.

    You know the mass percentage of it in the solution => you know the mass of the solution containing the required amount of ferric chloride.

    Can you see what happens next?
  6. Sep 12, 2012 #5
    muultiply mass by mass percentage?
  7. Sep 12, 2012 #6
    You do understand that the solution is partly water and partly ferric chloride, right?

    If, as voko pointed out, 100 gm of the solution contains 7 gm of ferric chloride, how many grams of solution contain 34 grams of ferric chloride?
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