Calculate the pH at the stoichiometric point of a titration of 25.0 mL of 0.120 M benzoic acid with 0.0230 M NaOH

Calculate mL NaOH needed to reach the equivalence point.

mLacid x Macid = mLNaOH x MNaOH

Let HBz = benzoic acid then
HBz + NaOH ==> NaBz + H2O

The pH at the equivalence point is determined by the hydrolysis of the salt, NaBz. The (NaBz) = molsNaBz/L = ?. I will call that z.

.......Bz^- + HOH --> HBz + OH^-
I......z...............0.....0
C......-x..............x.....x
E......z-x.............x.....x

Kb for Bz^- = (Kw/Ka for HBz) = (x)(x)/(z-x)
Substitute and solve for x = (OH^-) and convert that to pH.

To calculate the pH at the stoichiometric point of a titration, we need to determine the moles of benzoic acid and NaOH present.

Step 1: Calculate the moles of benzoic acid:
Moles of benzoic acid = volume (in liters) × molarity
Moles of benzoic acid = 0.0250 L × 0.120 mol/L

Step 2: Calculate the moles of NaOH:
Since benzoic acid and NaOH react in a 1:1 ratio, the moles of NaOH will be equal to the moles of benzoic acid.

Moles of NaOH = moles of benzoic acid = 0.0250 L × 0.120 mol/L

Step 3: Determine the volume of NaOH required to reach the stoichiometric point.
The stoichiometric point occurs when the moles of benzoic acid and NaOH are equal. Since we know the concentration of NaOH, we can calculate the volume required.

Moles of NaOH = 0.0250 L × 0.120 mol/L = 0.00300 mol

Volume of NaOH = Moles of NaOH / Molarity
Volume of NaOH = 0.00300 mol / 0.0230 mol/L

Step 4: Calculate the resulting solution volume at the stoichiometric point.
The volume of the benzoic acid solution is given as 25.0 mL. To this, we add the volume of NaOH required to reach the stoichiometric point.

Resulting solution volume = Volume of benzoic acid + Volume of NaOH
Resulting solution volume = 25.0 mL + calculated volume from step 3 (in mL)

Step 5: Calculate the concentration of the resulting solution at the stoichiometric point.
Since we know the moles of benzoic acid and the resulting solution volume, we can calculate the new concentration.

Concentration = Moles / Volume (in liters)
Concentration = moles of benzoic acid / (resulting solution volume in mL / 1000)

Step 6: Calculate the pOH at the stoichiometric point.
The pOH is calculated using the equation pOH = -log[OH-] where [OH-] is the hydroxide ion concentration.
In this case, since the stoichiometric point is reached, all of the benzoic acid has reacted with the NaOH, and the moles of OH- ions and volume can be directly calculated.

Moles of OH- ions = moles of NaOH = 0.00300 mol

Volume of resulting solution = resulting solution volume in mL / 1000

[OH-] concentration = Moles of OH- ions / Volume of resulting solution

pOH = -log[OH-]

Step 7: Calculate the pH at the stoichiometric point.
Since pH + pOH = 14, we can calculate the pH.

pH = 14 - pOH

Perform these calculations to find the pH at the stoichiometric point of the titration.