What is the molarity of H3PO4?

Question

A 50.00 mL mixture of H3PO4 and NaH2PO4 is titrated with 0.1050M NaOH. The first end point occurs at 5.07mL and the second end point occurs at 35.25mL.
a) what's the molarity of H3PO4
b) what's the molarity of NaH2PO4
c) what is the w/v% H3PO4

I need to know how this is done for a test please. thanks!

Answer 1

The 5.07 corresponds to just the H3PO4, so you can work out the moles and molarity of that.

The 35.25 refers to all the H3PO4 and NaH2PO4 moles added together, so by subtracting, you can work out what has reacted with just the NaH2PO4.