Calculate the pH of the acid solution

Question

An analytical chemist is titrating 189.7 mL of a 0.2900 M solution of butanoic acid (HC₃H₇CO₂) with a 0.6900M solution of NaOH. The pK_a of butanoic acid is 4.82. Calculate the pH of the acid solution after the chemist has added 92.86 mL of the NaOH solution to it.

you may assume the final volume equals the initial volume of the solution plus the volume of NaH solution added.

Round your answer to 2 decimal places.

Answer 1

This is the same as the previous question you posted. It is done the same way. I'll get you started, and hopefully you can complete it on your own.

HC₃H₇CO₂ + OH^- ==> H2O + C₃H₇CO₂^-

mols HC₃H₇CO₂ initially present = 189.7 ml x 1 L / 1000 ml x 0.2900 mol / L =

mols OH- initially present = 92.86 ml x 1 L / 1000 ml x 0.6900 mol / L =

Set up the ICE table:

HC₃H₇CO₂ + OH^- ==> H2O + C₃H₇CO₂^-

mols initial...mols initial.....0.............0...........Initial

-mols OH-...-mols OH-.............+mols OH-...Change

get values for equilibrium #mols..................Equilibrium

Find total volume = 189.7 ml + 92.86 ml and convert to liters

Calculate final concentrations

Use Henderson Hasselbalch equation to find pH