pH Adaptor & Electrode
13
Neutralisation of a strong base (sodium hydroxide) by a strong acid
(hydrochloric acid)
This experiment uses the pH sensor to monitor the pH as 0.1 mol dm
-3
hydrochloric acid is added to a
beaker containing 0.1 mol dm
-3
sodium hydroxide.
1.
Assemble the apparatus as shown.
2.
Carefully fill the burette with 0.1 mol dm
-3
hydrochloric acid. Place a beaker under the reservoir
and open the stopcock to allow a small amount of HCl to pass through. Pour the HCl from the
beaker back into the burette.
3.
Add 25 cm
3*
of 0.1 mol dm
-3
sodium hydroxide to the beaker and make sure the end of the pH
electrode is covered.
*Note: The volume of alkali may need to be increased, the solution should cover the bulb end of the pH
electrode. Do not remove the electrodes protective skirt - the end is made from permeable glass, which is
fragile and easily damaged
4.
Place a magnetic stir bar in the beaker and turn on the stirrer. Check the stir bar rotates freely
and does not make contact with the electrode.
5.
Open EasySense2 and select the Smart pH sensor
as the device and the Titration template from Lab
Setup.
Note: Lab Setup can be accessed on opening or via File -
> New Lab.
6.
Tap or click below the X axis and select Volume.
7.
Tap or click on Start to begin.
8.
Tap or click on
Take Sample
to record the first pH
value with no acid added.
Sodium hydroxide
0.5 to 2% (Solutions 0.05 to 0.5 mol dm
-3
)
Xi; R36/38
Wear pvc gloves and eye protection.
Sodium hydroxide solution is dangerous to eyes
Refer to Hazard Sheets for First Aid Measures
0.1 M HCl in burette
0.1 M NaOH
Magnetic stirrer
pH electrode
