From: glhurst@onr.com (Gerald L. Hurst) Newsgroups: sci.chem Subject: Re: normality Date: 14 Jan 1996 07:10:04 GMT In article <4d9ibb$14fp@bigblue.oit.unc.edu>, kferri@email.unc.edu (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 purposes. 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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