Chemistry

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The normality of 0.3 M phosphorus acid (H3PO3) is.......

• Chemistry -

Normality is Molar concentration divided by an equivalence factor. (n = c/f)

The hydrogen equivalence factor of an acid is the number of moles of acid that contains 1 mole of acidic hydrogen atoms.

The hydrogen equivalence factor of a triprotic acid is 1/3, so the normality of a triprotic acid is 3 times its molar concentration.

So for phosphorus acid: 0.3M = 0.9N

Any confusion felt during the reading of this explanation is one of the reasons the use of normality is depreciated in chemistry.

(Unfortunately it is still sometimes used in medicine.)

• Chemistry -

0.6

• Chemistry-doh. -

Doh! Right.

H3PO3 is diprotic, not triprotic like H3PO4.

• Chemistry -

I most certainly disagree with any statement that normality is not needed anymore although I agree it is confusing (sometimes) and its use has been discouraged since the IUPAC and a lot of smarter people than I am changed all the rules. (Yes, you hit a sore spot. I wish we still had normality.)
Second, I would like to point out to Aman that technically the question posed can't be answered without knowing the equation. Note that
H3PO3 + NaOH ==> NaH2PO3 + H2O and the factor is molar mass H3PO3/1 but for

H3PO3 + 2NaOH ==> Na2HPO3 + 2H2O the factor is molar mass H3PO3/2. That is the equivalent weight of a substance is the molar mass divided by the number of REPLACED H ions. Therefore, an acid like H3PO4 may have three different equivalent weights depending upon how many H ions are actually displaced in a reaction.

• Chemistry -

Chemistry sucks

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