The program allows the user to simulate the measurement of the conductivity of solutions composed of various cations and anions. Temperature and concentration of the solutions can be set by the user. The site also provides a discussion of conductivity, directions for running the simulation, two suggested experiments, and data sheets in pdf or html format for the basic experiment.
Type of Material:
Conductivity is presented as a simulation experiment through an interactive applet.
Recommended Uses:
This simulation can be used to help students understand the nature of weak acids and bases in terms of the extent of ionization and can also be used as an experiment method for estimating the acid or base ionization constant. Students can also investigate the conductivity of various ionic compounds and look for and explain deviations in conductivity patterns.
Technical Requirements:
None
Identify Major Learning Goals:
The basic experiment allow students to study 1) the concentration dependence of conductivity for silver nitrate solutions; 2) the donductivity of various ionic solutions of the same concentration; 3) the relative mobility of the 7 cations and the 5 anions. The advanced experiment allows students to estimate equilibrium constants for insoluble salts, a weak acid (acetic), and a weak base (ammonia) using conductivity measurements.
Target Student Population:
General chemistry students studying the conductivity of ionic solutions will benefit from this applet.
Prerequisite Knowledge or Skills:
Students should know what Molarity corresponds to, should know about the charges of ions, and how to correctly determine the formulae of salts from the anions and cations.
Content Quality
Rating:
Strengths:
Simulation is very easy to use. A discussion of conductivity is provided. Several experiments along with supporting data sheets are provided.
Concerns:
The simulation contains no covalent compounds, except for water. In our laboratory we measure the conductivity of several covalent species just to show that they are not conductors. Only acetic acid and ammonia are available as weak acids and bases. It might be useful to have additional acids available, for example phosphoric acid.
Potential Effectiveness as a Teaching Tool
Rating:
Strengths:
It is very helpful indeed to be able to specify the solution concentration and show how the conductivity changes, including being able to read absolute numbers off the conductivity meter. Plotting these vs. concentration should show the effects of ion pairing etc.
Concerns:
The failure to provide some non-conducting systems (i.e. pure water, ethanol, methanol etc.) detracts from an otherwise high quality and very useful applet.
Ease of Use for Both Students and Faculty
Rating:
Strengths:
The inclusion of a discussion as well as recommended experiments facilitates the use of this simulation for both students and faculty.
Concerns:
There are some issues with some of the links. Some of the links connect to a directory listing rather than a web page. This is somewhat disconcerting. Some of the links show up on the same window as the applet and the only way to remove them is to push the back button on the browser. In a distracting way, some links bring up a separate window. There is enough space within the applet to bring up helpful navigation items and discussions. The explanations for how to actually make the best use of the site, print out pdf files etc. is too sparse and unhelpful. This should be fixed.
Changing the concentration is painful. That should be enabled through an 'in the window' slider of some kind. There should be a simple reminder to push the button to measure the conductivity that disappears upon clicking on the left mouse. These are details that could be readily revealed by studying how first time users operate the web site.
Creative Commons:
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