Ways of Expressing Concentrations of Solutions © 2009, Prentice-Hall, Inc.

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 = © 2009, Prentice-Hall, Inc.

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 © 2009, Prentice-Hall, Inc.

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! © 2009, Prentice-Hall, Inc.

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. © 2009, Prentice-Hall, Inc.

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. © 2009, Prentice-Hall, Inc.

Changing Molarity to Molality If we know the density of the solution, we can calculate the molality from the molarity and vice versa. © 2009, Prentice-Hall, Inc.