The concentration of unknown H3PO4 solution is 0.052 M
<em> </em><u><em>calculation</em></u>
step 1: write the balanced molecular equation
3NaOH + H3PO4→ Na3PO4 +3H2O
step 2: find the moles of NaOH
moles = molarity x volume in liters
volume in liters = 7.12 ml /1000 = 0.00712 L
molarity = 0.1090 M = 0.1090 mol/l
moles is therefore = 0.1090 mol/L x 0.00712 L =0.00078 moles
step 3: use the mole ratio to determine the moles of H3PO4
H3Po4: NaOH is 3:1 therefore the moles of H3PO4
= 0.00078 x1/3 =0.00026 moles
Step 4: calculate the molarity of H3PO4
molarity = moles/volume in liters
volume in liters = 5.00 / 1000 =0.005 L
molarity is= 0.00026/0.005=0.052 M