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From: (Gerald L. Hurst)
Newsgroups: sci.chem
Subject: Re: normality
Date: 14 Jan 1996 07:10:04 GMT

In article <4d9ibb$>, (Karen
Ferri) says:

>Please pardon this basic question, but I can't recall the facts from my 
>college days and I can't find it in my old chemistry books:
>What is the definition of normality?  I need to make a 10 N (not M) NaOH 
>solution, but can't remember this definitiion.

You certainly came to the right forum with this question. Your
mailbox should overflow.

In the case of sodium hydroxide solution the normality and
molarity are the same because each mole of NaOH provides
one mole (or equivalent) of hydroxide ion. 

We arrive at a value for normality by looking at the number of 
equivalents each mole represents from the perspective of whatever 
reaction we are interested in.  We multiply the number of 
equivalents per mole times the molarity to get the normality.

Let's take HNO3 as an example. If we are dealing with an acid
base reaction we would say that one mole of the acid yields
one mole of hydronium ion so one mole is one equivalent and thus
the molarity and normality are equal. If we were using the 
same compound as an oxidizer such that the nitrogen went from
the 5+ oxidation state to the elemental nitrogen state of zero,
we would multiply the molarity of a solution by 5 to get the
the normality or number of equivalents per liter for oxidation

Most often we use normality to describe solutions of acids and
bases. This makes it very easy to figure out the number of
equivalents per mole. We merely count the active hydrogen
atoms in a molecule of acid or the number of hydroxyl radicals
associated with a molecule of base.

Jerry (Ico)

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