To obtain the solute for 205 g of a 18.7% (w/w) solution of sugar we would weigh out ________ g of sugar.?

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  • 3 weeks ago

    18.7% =( weight of solute/(weight of solute+weight of solvent))*100

    18.7/100 = ( weight of solute/(weight of solute+weight of solvent))

    0.187 = ( weight of solute/(weight of solute+weight of solvent))

       0.187 = weight of solute / 205g

      

    ∴ weight of solute = 0.187*205g

                                  = 38.335g

  • 18.7% of the 205g is sugar

    205 * 18.7 / 100 =>

    205 * 187 / 1000

    205 * 187 =>

    (200 + 5) * (200 - 13) =>

    200^2 + 5 * 200 - 13 * 200 - 65 =>

    40,000 + 200 * (5 - 13) - 65 =>

    40,000 + 200 * (-8) - 65 =>

    40,000 - 1600 - 65 =>

    38,400 - 65 =>

    38,335

    38335 / 1000 =>

    38.335

    to 3 sf

    38.3 grams

    205 - 38.3 =>

    205 - 40 + 1.7 =>

    165 + 1.7 =>

    166.7

    Conservation of mass says that the mass that goes in will be the mass that comes out.  Mixing 38.3 grams of sugar with 166.7 grams of water will give you 205 grams of solution that is 18.7% sugar by weight.

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