A 27.00 mL sample of an unknown H3PO4 solution is titrated with a 0.110 M NaOH solution. The equivalence point is reached when 25.78 mL of NaOH solution is added. What is the concentration of the unknown H3PO4 solution? The neutralization reaction is:

Question

H3PO4(aq) + 3NaOH(aq) -> 3H2O(l) + Na3PO4(aq)

Answer 1

I'm glad you wrote the equation; otherwise I wouldn't have known to which of the three equivalence point you titrated.
mols NaOH = M x L = ?
mols H3PO4 = 1/3 that (look at the coefficients)
M H3PO4 = mols H3PO4/L H3PO4.

Answer 2

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