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Homework Help: Calculate the mass of NaCl needed to bring sodium concentration to 0.139 M?

  1. Apr 30, 2012 #1
    A person suffering from Hypothermia has a sodium ion concentration in the blood of 0.114 M and a total blood volume of 5.1 L. What mass of sodium chloride needs to be added to the blood to bring sodium ion concentration up to 0.139 M? (assuming no change in blood volume)


    Atomic weight of Na: 230 g

    Mass of sodium in blood:
    230 x 0.114 M = 26.22 g

    Mass of sodium needed:
    230 x 0.139 = 32.97
    32.97 - 26.22 = 5.72 g

    5.72 g of sodium needed

    Ratio of mass in NaCl
    Mass of Cl : Mass of Nacl
    35.453 g : 230 g
    1 : 6.49

    Mass of Cl in NaCl when Na is 5.72 g:

    230/35.453 = 5.72/x
    230x = 5.72(35.453)
    230x = 202.79
    x = 202.79/230
    x = 0.88g

    Mass of NaCl needed:
    0.88g + 5.72g
    = 6.6 g

    Mass of NaCl needed 6.6g

    Is this correct?
  2. jcsd
  3. Apr 30, 2012 #2


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    Science Advisor

    Looks good. Although, I would have done the last calculation slightly differently:
    Mass of Cl : Mass of Nacl
    35.453 g : 230 g

    so the total mass of (one mol of) NaCl is 35.453+ 230= 265.453 g. That is a ratio of NaCl to Na of 265.453/230= 1.154 so the the total mass of NaCl to produce 5.72 g of sodium is (1.154)(5.72)= 6.6 g of NaCl. exactly what you got.
  4. Apr 30, 2012 #3
    Thank you very much:) I prefer your way haha

    If you're a yahoo question answerer, you can copy and paste that answer to the same question that I asked 3 times (no one wanted to answer) and I will give you best answer for each one:)
    thank you

    Here is the links to the same question:



    http://uk.answers.yahoo.com/question/index;_ylt=AiO70AMxfXqdmWoboJrzBPkgBgx.;_ylv=3?qid=20120430131115AA32Mjs [Broken]

    A lannister, always pays his debts.
    Last edited by a moderator: May 6, 2017
  5. Apr 30, 2012 #4
    Just realized I made a massive error in the atomic weight of Na, it's 23g not 230g hahaha
  6. May 1, 2012 #5


    User Avatar

    Staff: Mentor

    That was the first thing that caught my eye.
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