Part A: How many milliliters of 0.100 M NaOH are required to react completely wi
ID: 783071 • Letter: P
Question
Part A:
How many milliliters of 0.100 M NaOH are required to react completely with a sample of the solid carboxylic acid lactic acid, CH3CH(OH)COOH, with a mass of 0.1351 g (molar mass of lactic acid is 90.08 g/mol) The acid is monoprotic, only the last H dissociates.
Part B:
what is the pH of the resulting solution after the nuetralization reaction (that is after the required amount of NaOH is added to the lactic acid)? Use a Ka of .00014 for lactic acid and assume that the solid was dissolved in 15.0 mL of distilled water to prepare for titration.
All work needs to be shown. I know part B needs the henderson hasselbalch equation.
Explanation / Answer
A) let the volume be v.so,
equating the number of moles,
0.1*v*10^-3 =0.1351/90.08
or v=15 mL
B)pKa=3.85
since the salt is a salt of a strong base and a weak acid,
pH=7+0.5pKa+0.5log(concentration of the salt formed)
=7+0.5*3.85 +0.5log(0.1/2)
=8.27