Chemistry Reference
In-Depth Information
of the camera and the monitor. A few drops of sodium hydroxide solution
are to be added to both test tubes.
Observation: The precipitation of green respectively brown iron chloride
can be observed. The real colors of both precipitates can be compared on the
monitor.
E4.8. Large display of measured values on the computer screen
Problem: Digital measuring instruments with big numbers or with large
display are very expensive. The cheap solution for a large display of
measured values is the computer screen. An AD-converter and the appro-
priate software make it possible to connect regular measuring instruments to
the computer to display digital measured values.
Material: Computer and AD-converter, software, balance, Petri dish;
acetone (F).
Procedure: The balance is to be connected to the computer with the help
of the AD-converter. The large display of the measured values is to be
prepared with the appropriate software. A few drops of acetone are to be put
into the Petri dish, which is placed on the balance.
Observation: The measured values are displayed in a large format on the
screen. They show a decreasing mass of liquid acetone.
E4.9. Recording and processing of measured values with the computer
Problem: Some reactions are so fast that they cannot be recorded with
traditional methods. A neutralization reaction of an acidic with an alkaline
solution and recorded pH values can be realized with a connected computer:
one can easily capture the pH jump around the equivalence point. It might
be a good suggestion to let the students run some titrations and titration
curves in the traditional way, to compare them to the computer's way of
recording.
Material: Computer and software, connected AD-converter, calibrated
pH-meter with glass electrode, magnetic stirrer, Erlenmeyer flask, burette;
0.1 molar solutions of hydrochloric acid and sodium hydroxide (C).
Procedure: The pH-meter is to be connected to the computer via the
AD-converter; the titration is to be prepared with the appropriate software.
50 mL of hydrochloric acid are to be poured into the Erlenmeyer flask,
diluted with water, the magnetic stirrer is to be turned on, the electrode is to
be immersed and the titration is to be started with the sodium hydroxide
solution.
Observation: Before the titration the pH-value is 1.0. During the titration the
computer screen draws the titration curve. Adding 50 mL of sodium
hydroxide solution the pH value jumps near a pH of 7; after adding a few
more milliliters of sodium hydroxide solution pH 13 is almost reached.
E4.10. A model experiment as a medium for the car battery
Problem: The car battery should first be observed in a car and its function
may be discussed. The model experiment reproduces the processes of
charging and discharging and the reaction of the lead electrodes. Text
books or transparencies can be used to explain these processes.
