Question

A 35.00-mL sample of an unknown H3PO4 solution is titrated with a 0.130 M NaOH solution. The equivalence point is reached when 26.33 mL of NaOH solution is added. What is the concentration of the unknown H3PO4 solution? The neutralization reaction is: H3PO4(aq)+3NaOH(aq)→3H2O(l)+Na3PO4(aq)

Answer 1

Answer:

The concentration of the unknown H3PO4 solution is 0.0326 M

Explanation:

Step 1: Data given

Volume of the unknown H3PO4 solution = 35.00 mL

Molarity of NaOH solution = 0.130 M

The equivalence point is reached when 26.33 mL of NaOH solution is added.

Step 2: The balanced equation

H3PO4(aq) + 3NaOH(aq) → 3H2O(l) + Na3PO4(aq)

For 1 mole H3PO4, we need 3 moles NaOH to produce 3 moles of H2O and 1 mol of Na3PO4

Step 3: Calculate moles of NaOH

Moles NaOH = Molarity NaOH * volume

Moles NaOH = 0.130 M * 0.02633 = 0.0034229 moles NaOH

Step 4: Calculate moles of H3PO4

For 1 mole H3PO4, we need 3 moles NaOH to produce 3 moles of H2O and 1 mol of Na3PO4

 

For 0.0034229 moles NaOH, we have 0.0034229/3 = 0.00114 moles H3PO4 to react fully with the NaOH in the titrant.

 

Step 5: Calculate molarity of H3PO4

Molarity H3PO4 = moles H3PO4 / volume

Molarity H3PO4 = 0.00114 moles / 0.035 L

Molarity H3PO4 = 0.0326 M

The concentration of the unknown H3PO4 solution is 0.0326 M