Gizmo Equilibrium Concentration Student Lab Sheet

Name: Amanda Brito Date: Student Exploration: Equilibrium and Concentration Vocabulary: chemical equilibrium, concentration, equilibrium, equilibrium constant, reaction quotient, reversible reaction Prior Knowledge Questions (Do these BEFORE using the Gizmo.) Gary has $5,000 in his bank account and earns a modest salary. Every month he pays for rent, food, utilities, and entertainment. A. How will Gary’s account change if he saves more than he spends? B. C. How will Gary’s account change if he spends more than he saves? D. E. F. What happens if Gary spends exactly as much as he saves? G. Gizmo Warm-up If Gary spends exactly as much as he earns, his savings will be in equilibrium. Equilibrium occurs when two opposing processes occur at the same rate, leading to no net change. In the Equilibrium and Concentration Gizmo™, you will investigate how equilibrium can occur in chemical reactions. To begin, check that Reaction 1 is selected. Set Moles NO2 to 8 and Moles N2O4 to 0. 1. Click Play ( ) and observe the colliding molecules. What do you notice? the molecules move and collide. Occasionally there is a blue or red flash. 2. Click Reset ( ), and set Moles NO2 to 0 and Moles N2O4 to 8. Click Play. What do you notice now? 3. When a reaction can proceed in either direction, it is a reversible reaction. Based on what you have observed, is the synthesis of NO2 into N2O4 a reversible reaction? Explain. Question: What are the characteristics of reversible reactions? 1. Predict: Suppose you began with 8 moles of NO2 in the chamber. What do you think will happen if you let the reaction go for a long time? 2. Test: Click Play. Select the BAR CHART tab and check that Moles is selected. Observe the bar chart for about 30 seconds. As time goes by, what do you notice about the bars representing moles NO2 and moles N2O4? 3. Observe: Click Pause ( ). Select the GRAPH tab. Click the (–) zoom control on the horizontal axis until you can see the whole graph. What do you notice? This situation, in which the overall amounts of reactants and products does not change significantly over time, is called a 4. Record: On the BAR CHART tab, turn on Show data values. How many moles of NO2 and N2O4 are there right now? Moles NO2 Moles N2O4 5. Calculate: Suppose all the NO2 molecules were synthesized into N2O4. Given the equation 2NO2 ⇄ N2O4, how many moles of N2O4 would be produced 6. 7. Experiment: Click Reset. On the INITIAL SETTINGS tab, set Moles NO2 to 0 and Moles N2O4 to 4. Click Play. Click Pause when the bars of the bar chart stop moving very much. A. List the current amounts of each substance: Moles NO2 _ B. Moles N2O4 C. How do these results compare to starting with 8 moles of NO2? D. (Activity A continued on next page) Activity A (continued from previous page) 8. Summarize: In each trial, you started with the same amounts of nitrogen and oxygen. In this situation, did the equilibrium amounts change depending on the direction of the reaction? . 9. Set up the Gizmo: Click Reset and select the EXPERIMENT tab on the left. On the INITIAL SETTINGS tab on the right, select Reaction 2. Set Moles NO to 5, Moles NO2 to 5, and Moles N2O3 to 0. What are the reactants and product of this reaction? Reactants: Product: (Note: In this reaction, some of the NO2 reactants combine to form N2O4, as in reaction 1.) 10. Observe: Recall that a blue flash appears every time two reactants combine to form a product. A red flash appears every time a product dissociates into reactants. Click Play. ..........................................continued.................................................