Step 1
Rinse a cleaned
50 cm3
burette with about 5 cm3 of standardised 0.1 M NaOH solution. (Be sure to record the exact concentration of the NaOH if it is not exactly
0.1 M.) After rinsing, fill the burette with the 0.1 M NaOH solution about 2 cm3 above
the 0.0 cm3 mark. Use a clean and
dry funnel for filling. Tilting the burette at a 45° angle, slowly turn
the stopcock to allow the solution to fill the tip. Collect the excess solution dripping from
the tip into a beaker to be
discarded later. The air
bubbles must be completely removed from the tip. If you do not succeed the first time,
repeat it until the liquid in the burette forms one continuous column from top to bottom. Clamp the burette onto a ring stand (Fig. 1). By slowly opening the stopcock, allow
the bottom of the meniscus to drop to the 0.0 cm3 mark. Collect the excess solution dripping from the tip into a
beaker to be discarded later. Read the meniscus carefully to the nearest 0.1 cm3 (Fig. 2).
Figure 1. Titration setup.
Figure 2. Reading the meniscus.
17.58 cm3 – incorrect
17 cm3 – incorrect
17.5 cm3 – correct
Step 2
With the aid of a 5 cm3 volumetric pipette, add 5 cm3
of vinegar to a 100 cm3
conical
flask. Allow the vinegar to drain completely from the pipette by holding the pipette in such a manner that its tip touches the wall of the flask.
Record the volume of the vinegar added, and the initial volume of the NaOH in
the burette. Add a few drops of phenolphthalein indicator to the
flask and about 10 cm3 of distilled water.
The distilled water is added to dilute
the natural color that some commercial vinegars have. In this way, the natural color
will not interfere with the color change of the indicator.
Step 3
While holding the neck of the conical flask in your left hand and swirling it, open
the stopcock of the burette slightly with your right hand and allow the dropwise addition of the NaOH to the flask. At the point where the NaOH hits the vinegar solution the color may temporarily turn pink, but this color will disappear
upon mixing the solution by swirling. Continue the titration until a faint permanent
pink coloration appears. Stop the titration. Record the volume of the NaOH in your burette. Read the meniscus to the nearest 0.1 cm3 (Fig. 2).
Step 4
Repeat the procedures
in steps 1–3 until consistent
values are obtained.
