Note that reactions 1 and 4 are identical and will only need to be performed

Note that reactions 1 and 4 are identical and will

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with each other to confirm Hess’s law. Note that reactions 1 and 4 are identical and will only need to be performed once. Reagents and Supplies Solid sodium hydroxide, 1.0 M NaOH, 1.0 M HCl, 1.0 M CH 3 COOH (See posted Material Safety Data Sheets) Vernier kit with a temperature probe (from stockroom), laptop computer (from the lab)
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3 Procedure 1. Obtain a Vernier kit containing a temperature probe and a Styrofoam cup with a lid from the stockroom. Obtain a laptop computer from the instructor. 2. Connect the Vernier kit and the laptop computer according to instructions provided in Appendix A. 3. Rinse the temperature probe with deionized water and wipe dry with a paper towel. 4. Set up the temperature probe and the Styrofoam cup as shown in the picture below. The Styrofoam cup should be placed inside a large beaker. R EACTION 1 5. Measure exactly 100.0 mL of deionized water and add into the Styrofoam cup. Place the temperature probe in the liquid for one or two minutes to allow the probe to reach thermal equilibrium with the solution. 6. Measure about 2.0000 grams of solid sodium hydroxide (about 20 pellets) and record the exact mass. The mass will not be exactly two grams, but it should be as close as possible without breaking the pellets. Make sure to clean up any spills immediately. Make certain step 5 is complete before weighing the sodium hydroxide. Sodium hydroxide is hygroscopic and will absorb water from the air quickly. 7. Click the “collect” button on the computer. 8. After 2-3 seconds of temperature collection add the solid sodium hydroxide into the Styrofoam cup and mix the contents to dissolve the pellets in the water.
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4 9. The temperature will begin to increase and reach a maximum value and then begin to plateau. When the temperature stays at this point for at least 30 seconds stop the collection and click the STAT button found on the menu bar above the graph. Record the minimum and maximum temperature as T i and T f. Calculate T. 10. Dispose the contents of the Styrofoam cup into a large beaker and label this beaker as the “waste”. 11. Rinse the Styrofoam cup and the temperature probe with deionized water and prepare for the next reaction. R EACTION 2 12. Measure exactly 50.0 mL of deionized water and 50.0 mL of 1.0M HCl and add both into the Styrofoam cup. Place the temperature probe inside the beaker and allow it reach thermal equilibrium. 13. Measure about 2.0000 grams of solid sodium hydroxide (about 20 pellets) and record the exact mass. The mass will not be exactly two grams, but it should be as close as possible without breaking the pellets. Make sure to clean up any spills immediately. Make certain step 12 is complete before weighing the sodium hydroxide. Sodium hydroxide is hygroscopic and will absorb water from the air quickly. 14. Click the “collect” button on the computer. 15. After 2-3 seconds of temperature collection add the solid sodium hydroxide into the Styrofoam cup and mix the contents to dissolve the pellets in the solution.
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