What is the molarity of h3po4 if 15.0 mL is completely neutralized by 38.5 mL of 0.150M naoh?

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Answer 1 · 2018-04-22T22:00:27

This one will be controversial....

We address the acid-base rxn:

#H_3PO_4(aq) + 2NaOH(aq) rarr Na_2HPO_4(aq) + 2H_2O(l)#

And with respect to sodium hydroxide, we gots....

#38.5*mLxx10^-3*L*mL^-1xx0.150*mol*L^-1=5.775xx10^-3*mol#...

And there are HALF this molar quantity OF PHOSPHORIC ACID in the #15.0*mL# initial volume...and so we gots....

#[H_3PO_4]=(1/2xx5.775xx10^-3*mol)/(15xx10^-3*L)=0.1925*mol*L^-1.#

Again, I remind you that phosphoric acid is NOT a triacid....look at this site.