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VIRTUAL CHEMISTRY LABORATORY - STOICHIOMETRY In this virtual lab exercise, you will do two experiments in the Virtual Chemistry

Laboratory. During your prelaboratory meeting, your instructor will give you a brief introduction to the use of the software you will use. You will not be given a specific procedure to follow for these experiments; instead, you will basically be designing your own experiments and will thus have to determine for yourself what procedural steps to take to accomplish the goals of the experiment. You must then record your procedures, data, etc. in an organized fashion. You must show any and all calculations on a separate sheet of paper for full credit. If you need it, there is a Help function at the top of the screen where you can get assistance with use of the software.

PROCEDURE

Part 1 - Oracle Problem

1. Open the Vlab (Virtual Chemistry Lab) and click on File, then Load Homework. 2. Expand the folder Stoichiometry and Limiting Reagents, and select the Oracle Problem. 3. Either double-click, or click and drag, the Problem Description on the left side of the

screen to the workbench (main area of the screen) and follow the instructions for the lab exercise.

4. Be sure to watch the Solution Information bar at the right side of the screen to view concentrations of all chemical species present at a given time.

You should combine all combinations of the four reagents two at a time, but only until you find a combination that gives a reaction, in order to determine the full stoichiometry of the reaction. Make sure you record exactly what procedures you followed, specify what glassware you used, including size, amounts of solutions used, etc., and record all of the results you obtain including units when you combine the reagents. Show your calculations and explain how you determined the stoichiometric coefficients in the balanced equation. In order to further support your conclusions, be sure to include concentrations of products and reactants present before and after each reaction combination that you use.

Part 2 - Oracle Problem 2

1. Open the Vlab again and click on File, then Load Homework. 2. Expand the folder Stoichiometry and Limiting Reagents, and select the Oracle Problem

2. 3. Either double-click, or click and drag, the Problem Description on the left side of the

screen to the workbench (main area of the screen) and follow the instructions for the lab exercise.

4. Be sure to watch the Solution Information bar at the right side of the screen to view concentrations of all chemical species present at a given time.

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Once again you should combine all combinations of the four reagents two at a time, but only until you find a combination that gives a reaction, in order to determine the full stoichiometry of the reaction. Make sure you record exactly what procedures you followed, specify what glassware you used, including size, amounts of solutions used, etc., and record all of the results you obtain including units when you combine the reagents. Show your calculations and explain how you determined the stoichiometric coefficients in the balanced equation. In order to further support your conclusions, be sure to include concentrations of products and reactants present before and after each reaction combination that you use.

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VIRTUAL CHEMISTRY LABORATORY - STOICHIOMETRY

Prelab Assignment

1. Consider the reaction between substances X and Y to produce substance Z. When 500. mL of 1.2 M X are combined with 500. mL of 1.2 M Y, the resulting concentrations after complete reaction are 0.40 M X and 0.40 M Z, but there is no Y remaining. Follow the steps below to determine the balanced chemical equation for this reaction.

a. Calculate how many moles each of X and Y are present before reaction occurs.

b. Now calculate how many moles of X and Z are present after reaction has occurred. (Remember that there is no Y remaining after reaction. Notice also that X and Z are now present in a total volume of 1000. mL.)

c. Since you now know how many moles of X were present before and after reaction

occurred, calculate how many moles of X have reacted. Then do similar calculations to determine how many moles of Y have reacted and how many moles of Z have been produced.

d. Knowing how many moles of each substance you started with and how many moles

remain after the reaction is done, you can now determine the stoichiometry of the reaction. Indicate your reasoning using complete sentences.