(FINAL) Chemistry Notebook 2016-17

The Learning Goal for this assignment is:
students will learn what properties are used to describe the nature of solutions
how to quantify the concentration of a solution.
Defining Concentration
Measures of Concentration
Concentration is defined as the amount of dissolved solute in a given amount of solvent or
solution. There are several terms that describe concentration. Some of these terms are relative;
that is, they can be used only to compare the concentration of one solution to another. Dilute and
concentrated are two such terms. A dilute solution contains less dissolved solute than a
concentrated solution (in equal volumes of solution).
The terms saturated, unsaturated, and supersaturated are terms that describe concentration more
precisely.
Saturated: The maximum amount of solute is dissolved in a given amount of solvent at a
particular temperature. Such solutions are stable.
Unsaturated: Less than the maximum amount of solute is dissolved in a given amount of
solvent at a particular temperature. Such solutions are stable.
Supersaturated: More than the maximum amount of solute is dissolved in a given amount of
solvent at a particular temperature. Such solutions are unstable.
Look at the solubility curve shown below:
The solubility of NaNO3 is 86.0 g/100 mL H2O (at 20 °C). If you
prepare a solution of 50.0 g NaNO3 dissolved in 100 mL H2O, an unsaturated solution results
(Point A on the graph).
continue adding NaNO to the solution until 86.0 g are dissolved, a saturated solution results
(Point B).
heat the solution to 50 °C, 113 grams NaNO3 can be dissolved (Point C). When the solution
cools back down to 20 °C, it will be supersaturated (Point D).
Quantifying Concentration
To describe the concentration of a solution even more precisely, various measures of concentration
can be used. Some of the ways concentration can be quantified include calculating the
Mass of solute per solution mass (expressed as a percent or parts per million)
Moles of solute per kilogram solvent (molality)
Mass of solute per liter of solution (grams/liter)
Moles of solute per liter of solution (molarity)
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