1. Ways of Expressing Concentrations of Solutions
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2. The concentration of a solution is the amount of solute present in given quantity of solvent Mass Percentage
mass of A in solution
total mass of solution
 100
Mass % of A =
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3. Parts per Million and Parts per Billion
Parts per Million (ppm)
mass of A in solution
total mass of solution
ppm =
 106
Parts per Billion (ppb)
mass of A in solution
total mass of solution
ppb =
 109
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4. total moles in solution
Mole Fraction (X)
moles of A
total moles in solution
XA =
In some applications, one needs the mole fraction of solvent, not solute — make sure you find the quantity you need!
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5. Molarity (M) mol of solute M = L of solution
You will recall this concentration measure from Chapter 4.
Since volume is temperature-dependent, molarity can change with temperature.
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6. Molality (m) mol of solute m = kg of solvent
Since both moles and mass do not change with temperature, molality (unlike molarity) is not temperature-dependent.
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7. Changing Molarity to Molality
If we know the density of the solution, we can calculate the molality from the molarity and vice versa.
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