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Homework Help: Ocean water is found to contain 7.2 g of NaCl, what is the molarity ?

  1. May 14, 2010 #1
    A 205 mL sample of ocean water is found to contain 7.2 g of NaCl, what is the molarity of the solution?
    (The problem also says, with respect to NaCl?)
    Ok, now, what do they mean with respect to NaCl?

    What is it usually in respect to?

    Anyways is this the correct way to do this?

    Recognize that NaCl is the solute, and the ocean water is the solution, then, you convert the 205 mL of ocean water to Liters and also you have to convert the 7.2 g of NaCl to mL, then L to add it with the ocean water because molarity is moles of solute divided by Liters of total solution isn't it? And then you just divide the solute converted into moles into that to determine the molarity?
     
  2. jcsd
  3. May 14, 2010 #2
    Please disclose the purpose of your inquiry...is this homework or a personal endeavor?
     
  4. May 15, 2010 #3
    In regards to your second paragraph, yes.

    Molar Mass of 7.2 g NaCl / Volume of water in litres. No need to convert NaCl to ml, as molarity is the moles of solute [any solute] within a given volume [usually 1 litre].
     
  5. May 15, 2010 #4

    Borek

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    Staff: Mentor

    Huh? I guess you meant something else.

    --
    methods
     
  6. May 15, 2010 #5

    Borek

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    Staff: Mentor

    There can be (and in sea water are) other salts dissolved, you are asked to calculate only molarity of the NaCl.

    205 mL is a total volume, you don't need any tricks to calculate it. Just convert 7.2g to moles of NaCl and divide as you wanted to.

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  7. May 15, 2010 #6
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