Part A - Determination of Concentration of
Unknown Base Solution
Obtain about 100 mL of base solution of unknown concentration in a clean
and dry 250 mL beaker. The oven may be used to dry the beaker.
Acclimatize the buret by rinsing the buret with two portions of base solution
of approximately 10 mL each portion. After rinsing, fill the buret to the
0.00 mL mark.
Obtain about 100 mL of standard acid solution in a clean
and dry 250 mL beaker. Write down the concentration of the acid solution
on the data sheet.
25.00 mL of standard acid, HCl, solution into a clean 125 mL Erlenmeyer
Erlenmeyer flask does not need to be dry as you will be rinsing the
flask with distilled water periodically.)
Add 2-3 drops of phenolphthalein indicator to the flask.
add the base solution to the acid solution until the end point is reached.
Read the buret carefully to determine the quantity of base used to reach
the end point. Record the volume of the base solution used.
#1 shows a good endpoint where the colour of the solution changes
to a pale pink colour.
#2 shows a bright pink endpoint. The brighter colour indicates that
the endpoint of this titration for flask #2 is farther away from the
equivalence point than flask #1.
Repeat steps 4 to 7 until two volumes of base solution are obtained. The
two volumes should agree to within 0.10 mL.