AP CHEM solutions
Several methods can express the concentration of a solute in a solution. Here are some of the most common:
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molarity (M): Moles of solute per liter of solution.
$ M = \frac{\text{moles of solute}}{\text{liters of solution}} $
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Molality (m): Moles of solute per kilogram of solvent.
$ m = \frac{\text{moles of solute}}{\text{kilograms of solvent}} $
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Mass Percent (%): Mass of solute divided by the total mass of the solution, multiplied by 100%.
$ %\text{ mass} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 100% $
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Mole Fraction ( $ \chi $ ): Moles of a component divided by the total moles of all components in the solution.
$ \chi_A = \frac{\text{moles of A}}{\text{total moles}} $
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Parts Per Million (ppm) and Parts Per Billion (ppb): Used for very dilute solutions.
$ \text{ppm} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 10^6 $
$ \text{ppb} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 10^9 $