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Experiment C-
Titration of a Strong Acid
and a Strong Base
Objectives
To study the titration process. To follow changes in the pH during the titration process while adding a strong base to a strong acid. To use a drop counter in order to get a pH versus volume (in drops) graph.
Modules and Sensors
PC + NeuLogTM^ software
USB-200 module
NUL-206 pH logger sensor
NUL- 223 Drop Counter logger sensor
Equipment and Accessories
Utility stand 1 Right angle clamp 2 Extension clamp 1 Burette 1 50 ml beaker 2 250 ml beaker 1 Pasteur pipette 1 Wash bottle 1 Plastic container 1
The items above are included in the NeuLog Utility accessories, UTL-KIT (only one right angle clamp is included).
Materials
50 ml of 0.05 M HCl 1 01 ml of 0.5 M NaOH 1 Water for the wash bottle 1 30 ml of pH 7 buffer solution 1
Introduction
Titration is an analytical tool to determine the concentration of an acid or basic solution. It is based on the neutralization process. Neutralization occurs when the hydronium ion from an acid interacts with a hydroxide ion from a base, on a one to one basis, forming water in the process. A salt is always a byproduct of this type of reaction. Titration is the progressive addition of an acid to a base, or vice-versa, to achieve neutralization. The point at which the acid and base are in equivalent amounts is called the equivalence or end point.
One common example for acid-base titration is the use of a hydrochloric acid solution, HCl, with a basic sodium hydroxide solution, NaOH. This is an example of a titration of a strong acid with a strong base.
In this experiment you will conduct a titration in which this reaction occurs. You will determine the equivalence point and plot a pH verses volume (in drops) graph.
HCl NaOH H 2 O NaCl
Sensor setup
- Connect the USB-200 module to the PC.
- Check that the pH and drop counter sensors are connected to the USB-200 module.
Note:
The following software functions are explained in short. It is recommended to practice the NeuLogTM^ software functions (as described in the user manual) beforehand.
- Run the NeuLogTM^ software and check that the sensors are identified.
Settings
- Click on the On-line experiment icon in the NeuLogTM main icon bar.
- Click on the Module setup icon on the drop counter sensor's module box to open a dialog box.
- Select the "Drops" radio button to change the sensor's mode.
- Close the Module setup dialog box.
- Click on the Experiment Setup icon (on the On-line sub-icon bar) and set the:
Experiment duration to 10 minutes Sampling rate to 20 per second
Module Setup
- When the solution reaches the 0 mark close the tap.
- Click on the drop counter Module setup icon , then click
on the Zeroing button. Notice that the drops in the drop counter window are reset to 0.
- Click on the Run experiment icon to start the measurement.
- Open the tap and adjust the drop rate to about 1-2 drops per second.
- Gently stir the HCl solution during the measurement by moving the beaker with your hand.
- Keep track of the volume of NaOH added to the HCl solution on your burette and also of the the pH change on the screen. When you see a sharp increase in the pH, write down the volume of the added NaOH solution in this stage.
- When the pH graph becomes constant, stop the experiment.
- Your graph should be similar to the following.
- Save your graph.
Click on the Experiment setup icon , click on the XY graph tab and choose sensor; then choose drop counter. You will get a graph of the pH of the solution against the added NaOH solution drops.
