Question

A 30.0 mL sample of an unknown H3PO4 solution is titrated with a 0.1M NaOH solution. The equivalence point is reached when 26.38 mL of NaOH solution is added. What is the concentration of the unknown H3PO4 solution?

The neutralization reaction is

H₃PO4 (aq)+ 3NaOH (aq) ----> 3H₂0 (l) +Na₃PO4 (aq)

Please guide me step by step and show your work

Answer 1

Balanced reaction equation H_3 PO_4 + 3 Naoh rightarrow Na_3 PO_4 + 3 H_2 O Lets calculate the moles of NaOH added using the volume and molarity of the NaOH volume of NaOH = 26.38 ml = 0.026381 moles = molarity times volume in liter = 0.1 m times 0.026381 = 0.002638 mol NaOH Now using the mole ration of the NaOH and H_3 PO_4 we can calculate the moles of H_3 PO_4 we can calculate the moles of H_3 PO_4. as follows Mole ratio is 3 mol middot NaOH = 1 mol H_3PO_4 0.002638 mol NaOH times 1 mol H_3PO_4/3 mol NaOH = 0.0008793 mol H_3PO_4 Now using the moles and volume of H_3PO_4 we can calculate its molarity volume of H_3PO_4 used = 30.00 ml = 0.0300 L molarity = moles/ volume in liter = 0.0008793 mol/0.030 l = 0.0293 m