LAB: Titration of a Weak Acid with a Strong Base
(DCP, optional CE)
In this lab, you will determine which unknown weak acid you are titrating based on the data in the
table below. Titrate 100.0 mL (measured with a volumetric flask) of the unknown acid (made by your
instructor by measuring out 4.00 g of the solid anhydrous acid and diluting to 1000.0 mL in a
volumetric flask) with aqueous 0.10 M NaOH. You will use the PASCO GLX, along with a pH sensor
and drop counter, to obtain appropriate measurements during the titration. You will need to
calibrate each sensor before use. It may be a good idea to also use an acid-base indicator, such as
phenolphthalein, in order to make qualitative observations in addition to quantitative measurements
during your lab.
Table 1: Unknown Acid Information
Name
Formula of
most common
form
Glycolic acid
HC2H3O3
Equivalent
Mass
(g/mol)
76.05
Ka
pKa
1.6 x 10-4
3.80
Potassium dihydrogen
phosphate
Potassium hydrogen sulfate
KH2PO4
136.09
Ka2 of H3PO4 = 6.2 x 10-8
7.21
KHSO4
136.17
Ka2 of H2SO4 = 1.2 x 10-2
1.92
Potassium hydrogen sulfite
KHSO3
120.16
Ka2 of H2SO3 = 6.4 x 10-8
7.19
Sodium dihydrogen
phosphate
Sodium hydrogen sulfate
NaH2PO4H2O
138.01
Ka2 of H3PO4 = 6.2 x 10-8
7.21
NaHSO4H2O
138.08
Ka2 of H2SO4 = 1.2 x 10-2
1.92
Sodium hydrogen sulfite
NaHSO3
104.07
Ka2 of H2SO3 = 6.4 x 10-8
7.19
Potassium hydrogen
tartrate
KHC4H4O6
188.18
Ka2 of H2C4H4O6 = 4.6 x 10-5
4.34
Lab #17