When punching in a long equation into our calculator, we may often run into syntax or calculation errors by forgetting to close our parentheses or pressing the wrong buttons. Creating calculator programs can help decrease these errors, specifically when trying to find the change in enthalpy at constant pressure. This idea can be applied to other equations that may be used often yet tedious to type out.

Part 1 of 3:
Before Beginning the Program

  1. 1
    Learn the overall layout of the calculator buttons.
    • The 2ND button is used to access the functions that are in blue and to the left above each button.
    • The ALPHA button is used to access the letters and symbols that are in green and to the right above each button.

    Tip: A-LOCK mode (2ND+ALPHA) may be used to enter multiple letters without having to click ALPHA after every letter pressed.

  2. 2
    Analyze the equation. Determine the number and type of variables that are needed to plug into the calculator.
    • In this example, there are 2 variables that need to be assigned a value: initial and final temperature and 4 heat capacity constants for a specific compound (a, b, c, d).

    Note: X isn't assigned a value because the equation is integrating with respect to x.


Part 2 of 3:
Creating the Program

  1. 1
    Create a new program. Press PRGM, then press the right arrow > twice to New. Hit ENTER.
  2. 2
    Type and enter a name. Use a name that describes the program. Enthalpy change can also be denoted as DELTAH.

    Note: The calculator will automatically be in A-LOCK mode because the name of the program can only contain letters. Numbers or symbols will cause a syntax error.

  3. 3
    Create a user input with a prompt for the initial temperature. A prompt what is shown to the user when they are executing the program.
    • Press PRGM, I/O tab, then Input.
    • Begin a prompt by pressing ALPHA + + to add the first quotation mark.
    • Type out the prompt, such as T INITIAL, for the initial temperature, using ALPHA or A-LOCK mode. The prompt may as descriptive as you'd like.
    • Complete the prompt by pressing ALPHA + + again to add the ending quotation mark.

    Tip: Add a colon : and space (ALPHA+0) at the end of the prompt to separate the prompt and the input.

  4. 4
    Store the user input into an assigned variable. Insert a comma using the , button. Choose a single letter as the variable, like "I" for initial temperature, to store the inputted value. Press ENTER to begin a new line.

    Tip: Line breaks help organize programs. Use wisely as they may interrupt the execution of the program.

  5. 5
    Repeat Steps 3 and 4 for the final temperature. Choose a unique letter for all of the assigned variables.

    Note: If a letter is repeated, a new value will be stored in that letter.

  6. 6
    Create a prompt command for the a constant. Press PRGM, I/O tab, then Prompt. Choose a single letter as the constant, such as a for the a constant. Press ENTER to begin a new line.
  7. 7
    Repeat Step 6 for the other three constants: b, c, d.
  8. 8
    Add the equation into the program. Insert the function carefully and accurately. You do not want to create a program that spits out a wrong answer. This is the time where syntax really matters, so that you don't have to worry about it in the future.
    • Press MATH + 9 to access the definite integral function fnInt(. The syntax for this function is fnInt(function, variable, lower limit, upper limit).
    • Insert the function accordingly, incorporating the assigned variables from step 6. Do not forget the x variable.
    • Put a comma , at the end of the function. Add the variable x using ALPHA+STO> and a comma ,. Add the initial temperature variable (ex. I) for the lower limit with a comma ,. Add the final temperature variable (ex. F) for the lower limit with a comma ,.
    • Close the function with the right parenthesis: ).

    Tip: EE may be used in place of

    10^ . This can be accessed by pressing 2ND + ,.

  9. 9
    Store the result into a variable. Press STO>, then another unique letter (ex. H).
  10. 10
    Line break and display the result. Press ENTER, PRGM, and then go to I/O. Then go to Disp. Insert the variable that was chosen for Step 9 and press ENTER.
  11. 11
    Return to the home screen through 2ND + MODE. The program will automatically save.

Part 3 of 3:
Executing the Program

  1. 1
    Press PRGM.
  2. 2
    Select the program.
  3. 3
    Press ENTER. The prompts will show up one by one.
  4. 4
    Enter the value for each variable. In the image, the heat capacity constants for propane gas were used.
  5. 5
    Receive your result. The result shown is the enthalpy change (kJ/mol) at constant pressure for propane gas from 25 to 100 Celsius.

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      About This Article

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      Co-authors: 3
      Updated: February 8, 2020
      Views: 661
      Categories: Calculators

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