# Programs for TI-83plus/TI-84plus Calculators

The TI-83plus/TI-84plus graphing calculators are used extensively in our AP Chemistry program. They are used in conjunction with the lab component, where we do many labs with the Vernier LabPro and Vernier probes. In addition, many calculations can be simplified (once the theory is mastered) by use of calculator programs. Below I have linked to some useful programs, most of which I have written or modified. All of the programs are are in zip archives, with a simple readme file. You will need an unzipping program, and a TI link cable and the TI-Connect program for your computer.

Please remember that no program is a substitute for comprehension of underlying theory. I am confident that the programs are sound. However, as my father was fond of saying, "The tool is only as good as the person operating it." Use at your own risk. Also, understand that the College Board is fully aware of the existence of programs such as these, which is one of the reasons why the AP tests are shifting from rote application of calculations to discussion and explanation of the theories at work.

### Electrochemistry

Electrochemistry designed to solve problems involving the Nernst equation as well as electolytic metal plating. The Nernst equation sub-program can solve the Nernst Equation for Standard Electrode Potential (E^{0}), actual potential (E), number of moles of electrons (n), reaction quotient (Q), and temperature in Kelvins. The form of the Nernst equation used is E = E^{0} - (RTlnQ)/(nF).

The second subprogram solves electroplating problems. It is capable of calculating time required for plating, amperes required for plating, moles of electrons transferred, moles of metal plated, grams of metal plated, and molar mass of the metal plated. When the program asks for the ionic charge of the metal, you must enter the number of electrons that are gained by the metal when it is reduced at the cathode. For instance, in the conversion of Al3+ ion to elemental aluminum, you would enter "3" as the ionic charge (without the quotes!)

### Gas Laws

GASLAWS is designed to solve Charles Law, Boyle's Law, The Combined Law, and The Ideal Gas Law. The work is a modification of programming already done by Bisun and Mad Melvin, as posted at the Ti.calc ftp site. I greatly appreciate their original work, which helped me in organizing my thoughts and formulas. Changes made include asking the user to choose whether you are using atmospheres or kilopascals, and then the allowing the program to solve for the correct variation of the gas constant, R. The ideal gas law can now solve for Molecular weight of an unknown gas. In addition, the Charles, Boyles, and Combined laws will solve for either original (V_{1}, P_{1}, T_{1}) or new (V_{2}, P_{2}, T_{2}) conditions.

### Buffers

BUFFERS solves the various permutations of the Henderson Hasselbalch equation. You choose between problems focused on pH and Ka, or pOH and Kb. The program then solves for pH, pOH, Ka, Kb, [acid], [base], or [base]/[acid]. The program has worked perfectly for my AP students during the 2001 year. None-the-less, use the program at your own risk, and understand that answers are only as good as the data that you enter.

### Titrations

TITRATE is a program from "Modeling Titration Curves" in the Spring 1997 issue of Eightysomething! I obtained this from the Ti.calc ftp site and have found it to be an excellent tool for examining the effect of *K _{a}*,

*K*,

_{b}*K*and concentration on titration curves. The program even allows you to save images for the graphs that are generated, which can be exported for use in word processors.

_{w}### Rate Laws

RATELAWS allows you to select either zero order, first order, or second order reaction type, and the program gives the form of the integrated rate law for that order, the relationship between time and concentration that yields a linear relationship, and the equation for calculating the half-life. If you have data for the time and concentration relationship of a particular reactant, you should enter the time data into L_{1} (list 1) and the concentration data into L_{2} (list 2) PRIOR to beginning the program. If this has been done, you can opt to have a regression analysis done on the list data, with statistical diagnostics performed. The program will turn on your calculator's diagnostics for you. The diagnostics will give you the correlation coefficient, r, for the linear relationship between time and the variation of the concentration for that order reaction. Diagnostics will also give r^{2}, the coefficient of determination. Simply put, the closer these diagnostic values are to 1.000, the more closely the data adheres to a linear relationship.
However, it will only do one analysis per "pass" through the program. Simply hit **ENTER** after one regression analysis to return to the start of the program and continue your analyses for the other orders.

### pH

pH is designed to solve pH related problems. If you know pH, it calculates pOH, [H^{+}], and [OH^{-}]. If you know pOH, it calculates pH, [H^{+}], and [OH^{-}]. If you know [H^{+}], it calculates pH, pOH, and [OH^{-}]. If you know [OH^{-}], it calculates pH, pOH, and [H^{+}].
The assumption is that Kw is 1.0 x 10^{-14}, the temperature of the solution being 25ºC, and the solution being relatively dilute (no concentrations of 1 molar or greater).

### Quadratic Equations

QUADRAT is designed to solve the the quadratic equation. It should be particularly handy in solving for equilibrium problems that do not lend themselves to simplification. The answer will be generated for both possible solutions, (+) or (-).