practice exam...not sure how to do this

A solution contains 10.0 mmol of H3PO4 and 5.0 mmol of NaH2PO4. How many millimeters of 0.10 M NaOH must be added to reach the second equivilence point of the titration of the H3PO4 with NaOH?

It will take 10 mmols NaOH to convert 10 mmoles H3PO4 to NaH2PO4 and another 10 to convert to Na2HPO4 plus 5 mmoles to convert 5 mmole NaH2PO4 to Na2HPO4. That's a total of 25 mmoles needed. You hav e 0.1M NaOH, M = mmoles/mL. Substitute and solve for mL. NOTE: it's milliliters and not millimeters. Millimeters is a unit of length.

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To determine the amount of 0.10 M NaOH needed to reach the second equivalence point of the titration of H3PO4, we need to calculate the number of millimoles of H3PO4 present in the solution.

1. Find the total number of millimoles of H3PO4 in the solution:
- H3PO4: 10.0 mmol
- NaH2PO4: 5.0 mmol

2. Determine the reaction stoichiometry between H3PO4 and NaOH:
The balanced equation for the reaction is:
H3PO4 + 3NaOH -> Na3PO4 + 3H2O

From the equation, we see that 1 mole of H3PO4 reacts with 3 moles of NaOH.

3. Calculate the number of moles of H3PO4 reacting in excess:
Since the second equivalence point is reached, it means both H3PO4 and NaH2PO4 have reacted. Therefore, the amount remaining is given by:
Remaining H3PO4 (mmol) = Initial H3PO4 (mmol) - moles of H3PO4 that reacted with NaH2PO4 (mmol)
Remaining H3PO4 (mmol) = 10.0 mmol - 5.0 mmol = 5.0 mmol

4. Calculate the number of moles of NaOH required to react with the remaining H3PO4:
Moles of NaOH (mmol) = Moles of H3PO4 (mmol) / Reaction stoichiometry
Moles of NaOH (mmol) = 5.0 mmol / 1 = 5.0 mmol

5. Calculate the volume of 0.10 M NaOH required:
Volume of NaOH (mL) = Moles of NaOH (mmol) / NaOH concentration (mol/L) * 1000
Volume of NaOH (mL) = 5.0 mmol / 0.10 mol/L * 1000 = 500 mL

Therefore, you would need to add 500 mL of 0.10 M NaOH to reach the second equivalence point of the titration of H3PO4 with NaOH.

To determine the number of millimeters of 0.10 M NaOH needed to reach the second equivalence point of the titration, you need to understand the stoichiometry of the reaction between H3PO4 and NaOH. Let's break it down step by step:

Step 1: Determine the balanced chemical equation for the reaction between H3PO4 and NaOH.
The equation is: H3PO4 + 3NaOH → Na3PO4 + 3H2O
This balanced equation tells us that one mole of H3PO4 reacts with 3 moles of NaOH.

Step 2: Calculate the number of moles of H3PO4 available.
Given: 10.0 mmol of H3PO4
Since 1 mole = 1000 mmol, we can convert:
10.0 mmol / 1000 = 0.0100 moles of H3PO4

Step 3: Determine the number of moles of NaOH needed.
Since the stoichiometric ratio between H3PO4 and NaOH is 1:3, we can determine the moles of NaOH needed:
0.0100 moles of H3PO4 x (3 moles of NaOH / 1 mole of H3PO4) = 0.0300 moles of NaOH

Step 4: Calculate the volume of 0.10 M NaOH required.
Using the formula:
moles = concentration x volume
We can rearrange the formula to solve for the volume:
volume = moles / concentration
Given:
concentration of NaOH = 0.10 M
moles of NaOH = 0.0300 moles

volume = 0.0300 moles / 0.10 M = 0.300 L
Since 1 L = 1000 mL, we can convert:
0.300 L x (1000 mL / 1 L) = 300 mL

Therefore, you will need to add 300 milliliters of 0.10 M NaOH to reach the second equivalence point of the titration.