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Homework Help: Mass range

  1. Sep 8, 2008 #1
    1. The problem statement, all variables and given/known data
    Brass is an alloy of copper and zinc. Varying the mass percentages of the two metals produces brasses with different properties. A brass called yellow zinc has high ductility and strength and is 34%-37% zinc by mass.
    (a) Find the mass range (in g) of copper in 185 g of yellow zinc.
    (b) What is the mass range (in g) of zinc in a sample of yellow zinc that contains 46.5 g of copper?

    2. Relevant equations
    No specific formulas

    3. The attempt at a solution
    I got part (a), This is what I did roughly
    (185 g)(.34) = 62.9 g of zinc 185 g - 62.9 g = 122.1 g of copper
    (185 g)(.37) = 68.45 g of zinc 185 g - 68.45 g = 116.55 g of copper

    Mass range = 116.55 g - 122.1 g of copper

    I think that's correct. Now I just have no idea how to do part (b), there is no mass range for copper, just one number, 46.5.

    Any ideas? Thanks guys :)
  2. jcsd
  3. Sep 9, 2008 #2


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    Staff: Mentor

    If total is 100% and Zn is 34%-37%, how much is Cu?
  4. Sep 9, 2008 #3
    Ah I see, I think I got it now. I work backwards using an average percentage and actual mass value to get the total mass of the yellow zinc. Thank you!
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