How can I calculate Molarity?

by Guest8270  |  11 years, 4 month(s) ago

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If 21.25 g of silver nitrate AgNO3, are dissolved with 500 mL of water, what is the Molarity of the resulting solution? What is the ppm of the solution?

 Tags: calculate, molarity



  1. Tom Reeds

    Molarity is a way of expressing the concentration of any solution. It is defined as number of moles which are dissolved in one litre of solution and it is also known as moles per litre. Rather than writing moles per litre, it is abbreviated by M, and it means moles per litre not just moles. There is a difference between moles and molarity. Molarity measures the concentration of the material.
    Molarity is calculated by the following formula,
    It is
    Molarity = Grams/ (Molecular Weight x Volume)
    While the formula for moles is Moles/liter = Grams/{ (grams/mole) x liters}

  2. Guest8387
    well 500mL is the final volume you can assume that adding silver nitrate doesn't change the volume because it is dissolved, i.e. lives in the intermolecular spaces of water, it actually dissociates into ions. So 500mL is the final volume.

    the mol wt of silver nitrate is :169.87

    # moles= mass/molecular weight

    = 21.25/169.87 =0.1258....

    Molarity is moles per L

    If 0.1258 moles are in 500 mL

    0.1258 * 2 are in 1000mL

    so the answer is 0.2517.... or 0.25M (2dp)
  3. Guest7596
    Since it's listing it in terms of grams, chances are that it is solid AgNO3. Since this is the case, you can probably just consider 500 mL as the final volume.
  4. Guest3934
    21.25 grams/169.9 grams/mol/0.5 liters = 0.2501 M

    parts per million = mg /liter = ug/mL

    so if there are 21.25 grams in 500mL then there are 42.5 grams in a liter 42.5 grams = 42,500mg per liter =

    42,500 ppm

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