This MedLibrary.org supplementary page on Gram equivalent is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
In chemistry, a gram equivalent is the mass, in grams, of a compound's equivalent weight.
More formally, a gram equivalent of a substance taking part in a given reaction is the number of grams of the substance associated with the transfer of n electrons or protons or with the neutralization of n negative or positive charges, where n is Avogadro's number, 6.02×1023.
In a practical sense, a gram equivalent is the amount of a compound that is necessary to produce a given normality of a reactive species in a solution. Here, reactive species include ions that will precipitate, neutralize base (protons, H+), neutralize acid (hydroxide, OH-), donate electrons, or accept electrons.
To make clear the distinction between grams and gram equivalents, consider the following:
When making a solution with a given molarity, you measure grams of a compound and dissolve them in a known volume.
When making a solution with a given normality, you measure gram equivalents of a compound, in grams, and dissolve them in a known volume.
It is important to note that gram equivalents are specific to a given ion in solution (e.g., Na+, OH-, Ca2+, Fe3+, etc.), as measured in the solid state. As such, it can be a measure of ions participating in one of three general categories of reactions: oxidation-reduction reactions, acid-base reactions, and precipitation reactions:
- In acid-base chemistry, the gram equivalent expresses the mass of acid or base which will furnish a concentration of protons or hydroxide ions undergoing neutralization.
- In redox reactions, gram equivalents denote the mass of oxidizing or reducing agent that can accept or furnish a given molarity of electrons.
- In precipitation reactions, the gram equivalent is mass of a substance (typically a salt) which will produce a molar concentration of ions that participate in the precipitation.
References
- Meldrum, W.B. J. Chem. Ed., 1955, 32, 48.
Wikipedia content modification information:
- This page was last modified on 31 October 2007, at 16:35.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Gram equivalent".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.