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-   -   Need help finding Molarity (https://www.askmehelpdesk.com/showthread.php?t=507013)

  • Sep 12, 2010, 02:00 PM
    PrttyBrownEyez21
    Need help finding Molarity
    Were studying molarity in my bio class.I thought I knew what I was doing but it keeps saying my answers are wrong.

    Can someone tell me what I'm doing wrong?

    If you have 58 grams of NaCl in 1 (one) Liter of water, what is the molarity of the solution?

    -This is what I did. I found the molecular weight. Na was 22.990 and Cl was 35.353. I decided to round Na up to 23 and Cl to 35.5. Does the rounding affect that? After adding those togther you end up with 58.5.I then divided 58/58.5. I end up with 0.991453 so I rounded that to 0.991.Was that right?

    Another question I have is this

    This type of chemical solution resists changes in pH

    -I thought the answer to this was A buffer solution,but it said it was wrong. Is that right?
  • Sep 12, 2010, 03:32 PM
    DrBob1
    Both of your answers sound correct to me.
    Where are you getting the incorrect evaluation from?
    There are some trivial potential errors but nothing major except to a computer. For instance, the question may consider 58 g of NaCl to be one mole and therefore your answer of 0.991 is seen as wrong.
    Technically, to be 1.0 M you want 1 mole of NaCl dissolved in 1 liter of SOLUTION not in 1 L of water (because the solute will add to the total volume).
    Buffer solutions resist changes on pH.
    I say that you are correct!

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