This Web experiement illustrates the utility of the ICF Table to define and solve stoichiometric problems. An ICF Table has four rows (see example).

The balanced chemical equation for the reaction is displayed in the first row of the ICF Table. The second row contains the initial number of molecules or moles of each compound. The initial number of molecules or moles is the number of molecules or moles of the compound present in the container before the reaction occurs. This number of molecules or moles appears beneath the chemical formula for the compound.
    The third row in the ICF Table contains the changes in the numbers of molecules or moles of the reactants and products. These changes are the numbers of molecules or moles of reactants consumed and products formed during the reaction. Since molecules of reactants are consumed, the change in the number of molecules or moles of a reactant is a negative number. In the example above the entire four moles of O₂ are consumed (O₂ is the limiting reactant) and thus the change in moles of O₂ is - 4.00 moles. Also, the numbers of molecules or moles of reactants consumed and products formed are related by mole ratios e.g.


If the change in the number of molecules or moles of a reactant or product is known, then the changes in the numbers of molecules or moles of the other reactants and products can be calculated. In the example the changes in the numbers of moles of H₂O and NH₃ are determined from the change in the moles of O₂.



    The final numbers of molecules or moles, listed in the fourth row of the ICF Table, are the numbers of molecules or moles of reactants and products present in the container after the reaction occurs. The final number of molecules or moles of a compound is equal to the sum of the initial number of molecules or moles of the compound and the change in the number of molecules or moles of the compound e.g.


If the values for any two of the variables initial number of moles, change in number of moles , and final number of moles are known for one of the compounds, then the value for the third variable can be calculated. In the example above the initial number of moles of O₂ is 4.00 and the final number of moles of O₂ is 0.0 (O₂ is the limiting reactant). The change in the number of moles O₂ is then the difference between the final and inital numbers of moles.

    Enter the number of A molecules and the number of B molecules to be placed in the reaction container and click the "Start" button to initiate the reaction. When molecules of C are no longer formed, click the "Stop" button. The final number of A or B molecules is displayed above the reaction container. Click the button to access the ICF Table. A second window that contains the ICF Table will appear. Enter the initial numbers of A, B, and C molecules and the final number of A or B molecules in the Table. Use the concepts outlined above

to complete the Table. Click the button in the "ICF Table" window to obtain help or to verify that the entries in the Table are correct.

    Perform the experiments listed below and use the ICF Table to answer the questions. Please include a hard copy of each ICF Table. How to Obtain a Hard Copy of the Web Experiment.

1. How many molecules of C are produced when one molecule of A collides with one molecule of B?
2. Allow 5 A molecules to react with 5 B. How many molecules of C are produced?
3. Allow one dozen of A to react with a half of a dozen of B. How many dozens of C are produced?
4. Allow 5 molecules of A to react with 12 molecules of B. What is the change in the number of B molecules?

    If you have preformed all of the experiments, answered all of the questions, and completed the report to be submitted for credit, then you may check the Answers to ICF Table Questions