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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Xenonman on April 08, 2014, 10:14:45 PM

Title: Which solutions can have several normality values?
Post by: Xenonman on April 08, 2014, 10:14:45 PM

Hello all ;D
I just figured how annoying normality is. To get the full picture, I want to gather the names of as many solutions that have the same molarity, but different normality depending on the reaction they are used.
So far, I could think of Fe⁺³ ion, which could react to form either Fe⁺² or Fe_(s), thus having at least two normalities and one molarity. Same with copper.
The other one is H₂Y^-2: One could treat is as an usual acid or base (two acid/base sites per molecule), or use it for a typical complexometric titration (one complex is formed by one molecule). This gives at least two normalities and one molarity.

But I am sure there are examples I can't even think of. That's when all of you come in.

Title: Re: Which solutions can have several normality values?
Post by: Borek on April 09, 2014, 02:53:47 AM

H₂SO₄ (acid/base, BaSO₄ precipitation).

Pb²⁺ (precipitation of chloride, precipitation of sulfate)

MnO₄^- (three different values for oxidations in acidic, neutral and basic solutions)

And so on.

Title: Re: Which solutions can have several normality values?
Post by: Xenonman on April 09, 2014, 08:38:15 PM

Quote from: Borek on April 09, 2014, 02:53:47 AM

H₂SO₄ (acid/base, BaSO₄ precipitation).

I was taught sulphuric has two acid sites, and gets its two protons removed by bases and Ba²⁺, so its normality should be the same for both reactions.

Quote from: Borek on April 09, 2014, 02:53:47 AM

Pb²⁺ (precipitation of chloride, precipitation of sulfate)

Same thing here. Different stoichiometry, but same amount of positive charges and thus same normality.

Title: Re: Which solutions can have several normality values?
Post by: Arkcon on April 09, 2014, 08:48:00 PM

Xenonman:, you've made the same mistake twice in both postings.  Just because sthe sulfate ion is ^2-, doesn't mean it interacts twice, the same as two H⁺.  Likewise, the Fe²⁺ and Fe³⁺ don't enter into discussions of normality and molarity.

Title: Re: Which solutions can have several normality values?
Post by: Xenonman on April 23, 2014, 11:30:32 PM

Back from the dead.

As far as I understand, IUPAC mentions the viability of using equivalents for solutions part of redox reactions. Here: http://goldbook.iupac.org/E02192.html (http://goldbook.iupac.org/E02192.html).
And since equivalents are viable, and normality relies on equivalents, normality for redox should be a valid and archaic way of expressing concentration.