[itsme03]

a 200.0 mL sample of H₃PO₃ requires 22.50mL of 0.1250 M NaOH for the complete neutralization. what is the molarity of the H₃PO₃ solution?

the balanced equation is H₃PO₃ + 2NaOH  2H₂O + Na₂H₃PO₃

i tried just about everything, but the closest i got was .28 M
the answers .007 M

[Astrokel]

Check your product chemical formula again!

[itsme03]

i did. its right.

[Bioionic]

No, in your product should be a salt.

[itsme03]

i checked and that's what the book said the product's supposed to be. how do you know there should be a salt?

[Astrokel]

Generally an acid-base reaction gives salt and water or just salt. In acid-base reaction, the underlying reaction should be H⁺ from the acid reacting with OH^- from the base to give water.

Na₂H₃PO₃

This is wrong because complete neutralization means all the acidic hydrogen from your acid have reacted to become water, all it left in product should be just the anion.

[Bioionic]

Also remember the double replacement reaction.

AB + XY ---> AY + XB

[itsme03]

got it. thanks

[Bioionic]

Well... For other peeps that may be struggling with a similar problem.  Do you care to share your solution?  I always like to hear how someone else solves a problem.

I guess you did see the error in your original eq.