Question

How many mL of .452M H₃PO₄ solution are required to react completely with 75.0 mL of 0.205 M NaOH solution?

Answer 1

H3PO4 + 3NaOH -----------> Na3PO4 + 3H2O

According to the above balanced equation, 3 moles of NaOH is required to react completely with 1 mole of H3PO4.

No.of moles of NaOH = conc. x volume = 0.205 x (75/1000) = 0.0154 moles

No.of moles of H3PO4 = (1/3) no.of moles of NaOH = 0.0154 / 3 = 5.1 x 10^-3 moles

No.of moles of H3PO4 = conc. x volume

=> 5.1 x 10^-3 = 0.452 x volume

=> volume = 0.01128 L

=> volume = 11.28 mL <<<<<<<--------------(ANSWER)