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March 30, 2017

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how would I find the mass of something from the molality.....


How many grams of water should be added to 25.0 g of NaCl to produce a 0.450 m solution?

  • Chemistry - ,

    CC--Definitions, definitions, definitions.

    molality = moles/kg solvent

    You want 0.45 m and you want 25.0 g NaCl.
    How many moles is 25.0 g NaCl? That will be moles = grams/molar mass.
    25.0/58.5 (the 58.5 is an estimate) = 0.43 moles. Now substitute that into the definition for molal.
    0.45 m = 0.43 mols/kg
    solve for kg. (I rounded the 0.43 moles also).

  • Chemistry - ,

    I got it its 950 g

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