Solution Section Summary

In addition to molarity, a number of other solution concentration units are used in various applications. Percentage concentrations based on the solution components’ masses, volumes, or both are useful for expressing relatively high concentrations, whereas lower concentrations are conveniently expressed using ppm or ppb units. These units are popular in environmental, medical, and other fields where mole-based units such as molarity are not as commonly used.

Key Equations

Percent by mass = [latex] \frac{\text{mass of solute}}{\text{mass of solution}} [/latex] × 100
ppm = [latex] \frac{\text{mass solute}}{\text{mass solution}} × 10^6 [/latex] ppm
ppb = [latex] \frac{\text{mass solute}}{\text{mass solution}} × 10^9 [/latex] ppb


mass percentage (%w/w)
ratio of solute-to-solution mass expressed as a percentage
mass-volume percent
ratio of solute mass to solution volume, expressed as a percentage
parts per billion (ppb)
ratio of solute-to-solution mass multiplied by 109
parts per million (ppm)
ratio of solute-to-solution mass multiplied by 106
volume percentage
ratio of solute-to-solution volume expressed as a percentage