A 5.00-mL sample of an H3 PO4 solution of unknown concentration is titrated with a
0.1003 M NaOH solution. A volume of 6.55 mL of the NaOH solution was required to
reach the endpoint. What is the concentration of the unknown H3 PO4 solution?
To find the concentration of the unknown H3PO4 solution, we can set up a balanced chemical equation for the reaction between H3PO4 and NaOH:
H3PO4 + 3NaOH -> Na3PO4 + 3H2O
From the balanced equation, we can see that the ratio between H3PO4 and NaOH is 1:3. This means that for every 1 mole of H3PO4, we need 3 moles of NaOH to react completely.
First, let's calculate the number of moles of NaOH that reacted. We can use the equation:
moles of NaOH = volume of NaOH solution (in L) x molarity of NaOH solution
Given that the volume of NaOH solution required to reach the endpoint is 6.55 mL, we need to convert it to liters:
volume of NaOH solution (in L) = 6.55 mL / 1000 mL/L = 0.00655 L
Now, we can calculate the moles of NaOH:
moles of NaOH = 0.00655 L x 0.1003 mol/L = 0.000655 mol
Since the ratio between H3PO4 and NaOH is 1:3, the moles of H3PO4 must be one-third of the moles of NaOH:
moles of H3PO4 = 1/3 x moles of NaOH = 1/3 x 0.000655 mol = 0.000218 mol
Finally, we can calculate the concentration of the H3PO4 solution:
concentration of H3PO4 (in M) = moles of H3PO4 / volume of H3PO4 solution (in L)
Given that the volume of the H3PO4 solution is 5.00 mL, we need to convert it to liters:
volume of H3PO4 solution (in L) = 5.00 mL / 1000 mL/L = 0.00500 L
Now we can calculate the concentration of the H3PO4 solution:
concentration of H3PO4 (in M) = 0.000218 mol / 0.00500 L = 0.0436 M
Therefore, the concentration of the unknown H3PO4 solution is 0.0436 M.
Which end point? #1, #2, or #3.
We'll assume you titrated all of it.
H3PO4 + 3NaOH ==> Na3PO4 + 3H2O
mols NaOH = M x L = ?
Convert mols NaOH to mols H3PO4 using the coefficients in the balanced equation.
Then M H3PO4 = mols H3PO4/L H3PO4.