Using The TI-89 Equation Solver

If you have a TI-89 and your browser has an Acrobat reader, you might want to check out the complete chapter on the numeric solver in the guidebook.

Entering the Solver

Press [APPS]
Select option 9, Numeric Solver
 

Entering and Saving the Equation

Enter equation:  p*v=mol*Rg*t using [alpha] keys
Press [Enter] twice
To Save equation for later use, press [F1], Tools menu
Select option 2, Save copy asÖ
Type/Select Folder and/or FileName
 

Exit the Solver

To Exit Solver, Press [APPS] then
Select option 1, Exit
 

Solving the Equations

For the example above, here is what you should see: 

eqn:P*V=mol*Rg*T
 P=
 V=
 mol=
 Rg=
 T=
Some of these variables may have numbers after them, depending upon what already may be defined in your calculator. (The values will persist even after the calculator is turned off.)

Enter the values of all of the variables you know. Then go to the line for the variable you DON'T know and press [Clear] to erase whatever is there already and then [F2] to solve. We'll solve for volume (V) here: 

eqn:P*V=mol*Rg*T                         eqn:P*V=mol*Rg*T
 P=1                                               P=1
 V=                    Press [F2]==>      .V=22.40178759
 mol=1                                           mol=1
 Rg=0.08205783                             Rg=0.08205783
 T=273                                          T=273
 bound={-1.E14,1.E14}                     bound={-1.E14,1.E14}
 left-rt=0.                               left-rt=0.
Note that you can do math as you define your variables! For example, say you were given that the temperature was 15 oC. You could add 273 'on the fly': 
eqn:P*V=mol*Rg*T                         eqn:P*V=mol*Rg*T
 P=1                                               P=1
 V=                    Press [F2]==>     .V=23.63265504
 mol=1                                          mol=1
 Rg=.08205783                             Rg=.08205783
 T=15+273                                    T=288
 bound={-1.E14,1.E14}                     bound={-1.E14,1.E14}
Or maybe you want to solve for pressure, and the value you need is torr. For example,

What is the partial pressure of 1.0 mol of an ideal gas at 25oC if its volume is 2.0 L? 

eqn:P*V=mol*Rg*T                         eqn:P*V=mol*Rg*T
 P=                      Press [F2]==>    .P=12.22661667
 V=2                                              V=2
 mol=1                                           mol=1
 Rg=.08205783                             Rg=.08205783
 T=25+273                                    T=298
 bound={-1.E14,1.E14}                     bound={-1.E14,1.E14}
This pressure is in atmospheres, so we need to multiply
by the conversion factor "(760 torr)/(1 atm)": 
eqn:P*V=mol*Rg*T                         eqn:P*V=mol*Rg*T
.P=12.22661667*760      Press [Enter]==> .P=9292.2286692
 V=2                                              V=2
 mol=1                                           mol=1
 Rg=.08205783                             Rg=.08205783
 T=25+273                                    T=298
 bound={-1.E14,1.E14}                     bound={-1.E14,1.E14}
 

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