[will_L]

Is H3PO4 a triprotic or diprotic acid, if it is a triprotic acid, then how do we explain its reaction with sodium hydroxide?

 i.e. H3PO4 + 2NaOH == Na2HPO4 + 2H2O.

coz i thot it suppose2 take 3 mols of NaOH to react with 1 mol of H3PO4.

[JustinCh3m]

Yes, it's a triprotic acid and all "3 phases" of the acid's deprotonation are a weak acid reacting with the strong base (OH-).

OH- is a great base, so if it's in excess it will easily remove all 3 of phosphoric acid's 3 protons (H's)

[will_L]

do you mean in the execess of NaOH, Na2HPO4 will also be deprotonated?

[Borek]

Yes, if the pH of the solution is high enough, phosphoric acid is completely neutralized.

[will_L]

thanks very much.

[zakina]

Is H3PO4 a triprotic or diprotic acid, if it is a triprotic acid, then how do we explain its reaction with sodium hydroxide?

 i.e. H3PO4 + 2NaOH == Na2HPO4 + 2H2O.

coz i thot it suppose2 take 3 mols of NaOH to react with 1 mol of H3PO4.

2 H atoms have been replaced by 2 Na atoms. so net basicity increases due to Na so it is difficult for the 3RD H atom to be replaced by Na....this is what i think

[AWK]

so net basicity increases due to Na

?
Basicity of solution increase due to reaction:
HPO₄^2- + H₂O = H₂PO₄^- + OH^-
but HPO₄^2- is an amfiprotic ion then the secon reaction
HPO₄^2- + H₂O = PO₄^3- + H₃O⁺ also take place.