Common Units for Measuring Concentrations

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This Demonstration shows how to change units of a concentration by using appropriate conversion factors. The most common units are considered, except for mole fraction and molality, where there are no conversion factors. Initial and final units are given by clicking "from" and "to."


Units considered are:

• parts per billion (ppb)

• parts per million (ppm)

• percent by weight (% w/w)

• weight/volume percentage (% w/v)

• gram per litre (g/L)

• molarity (M)

• normality (N)

To convert we use:

• density of the solution ()

• density of the solute ()

• molecular mass of solute (M.M.)

• valence factor

The last item is the number of electrons exchanged in redox reactions or the number of of the acid (or the of the base) in acid-base reactions (n). [1]


Contributed by: D. Meliga, L. Lavagnino and S. Z. Lavagnino (December 2020)
Open content licensed under CC BY-NC-SA



Snapshot 1: conversion factors from parts per billion (ppb) to normality (N)

Snapshot 2: conversion factors from normality (N) to parts per billion (ppb)

Snapshot 3: conversion factors from parts per billion (ppb) to volume by volume (%v/v)


[1] P. M. Lausarot and G. A.Vaglio, Stechiometria per la Chimica generale, Padova, Italy: Piccin-Nuova Libraria S.p.A., 2005.

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