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Homework Help: Expressing concentrations as a percent

  1. Jan 26, 2017 #1
    • Please post this type of questions in HW section using the template and showing your work.
    You measure the concentration of O2 in seawater to be 5.0 mg O2/L H2O. Express this concentration as a percent.

    Question 2: The earths atmosphere contains 21% O2/L of air. How much more oxygen does the atmosphere hold than seawater from the previous question?

    So for question one I got 0.01% which I think is way off. For question 2, I was just going to subtract 21% from the answer from 1. I changed the milligrams to grams for question one.
  2. jcsd
  3. Jan 26, 2017 #2
    What was your attempt to solve #1?
  4. Jan 26, 2017 #3
    I converted the 1 5.0 mg to grams and got 0.005g. Then, I divided that by 50 which is the atomic msss for O2/L H2O I think and multiplied that by 100.
  5. Jan 26, 2017 #4
    Atomic mass of Oxygen is 16.00 amu, so O2 would be 32.00. Why did you divide by it though and then multiply by 100?
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