What is the concentration of a phosphoric acid solution of a 25.00 mL sample if the acid requires 42.24 mL of 0.135 M NaOH for neutralization?

Answer 1

H₃PO₄ + 3 NaOH --> Na₃PO₄ + 3H₂O

25.00 mL 42.24 mL

0.135 M

M = mol/volume (in Liters)

moles of NaOH = M x V = 0.00570 mol

0.00570 mol NaOH x 1 mol H₃PO₄ ⁄ 3mol NaOH = 0.00190 mol H₃PO₄

M_{H3PO4 =} 0.00190 mol ⁄ 0.02500L = 0.0760 M