Labs Endothermic versus Exothermic reactions, and Heat of Solution of NH4NO3 - Arnulfo Alejandro Mar

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Los Angeles Southwest College *

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038

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Chemistry

Date

Apr 30, 2024

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pdf

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8

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Endothermic vs. Exothermic In various chemical processes such as reactions and the dissolving of salts, heat is either absorbed or given off. We call these events either an endothermic (heat in) or exothermic (heat out) process. It is usual to detect these heat events by measuring the temperature change associated with the process. In this problem, you will dissolve several salts in water, measure the resulting temperature change, and then make deductions about the nature of the process. In this video we'll show you how to work with the balance to weigh out solids. 00:00 Calorimetry Lab Tips 1. To start this activity, click this link for Endothermic vs. Exothermic lab will load in a new tab. Click back to this tab to read further instructions and complete the questions below. You can follow along with the instructions below in the Procedures tab in the lab. from the list of assignments. The 2. There will be a bottle of sodium chloride (NaCl) on the lab bench. A weigh paper will be on the balance with approximately 2 g of NaCl on the paper. 3. The calorimeter will be on the lab bench and filled with 100 mL water. Make certain the stirrer is On (you should be able to see the shaft rotating). In the Thermometer section of the Live Data tray menu click Save Data to begin recording data. Allow 20-30 seconds to obtain a baseline temperature of the water. In this video we'll show you how to add salt to the calorimeter.
TBefore25 4. Drag the weigh paper with the sample to the calorimeter until it snaps into place and then pour the sample into the calorimeter. Observe the change in temperature until it reaches a minimum or maximum and then record data for an additional 20-30 seconds. (You can click on the clock on the wall labeled Accelerate to accelerate the time in the laboratory.) Click Stop Saving. Open the Lab Book menu in the tray. Record the temperature before adding the NaCl and the highest or lowest temperature after adding the NaCl below. TAfer 24.79 00:00 TBefore 25 5. Click the red disposal bucket or the Clear Lab button to clear the lab. Open the Presets menu in the tray and select the preset experiment called Heat of Solution-NaNO, and repeat the experiment with NaNO. Record the initial and final temperatures below. Calorimetry Lab Tips T ner23.95 TBefore 25 6. Click the red disposal bucket or the Clear Lab button to clear the lab. Open the Presets menu in the tray and select the preset experiment called Heat of Solution-NaAc and repeat the experiment with NaCH,COO (NaAc). Record the initial and final temperatures below. T Rer- 25.98
7. 4T NaC= -0.21 Calculate 4T (4T= TAfer-TBefore) for each mixture and record it below. 4T NaNO,= 1.05 4T NaCH,CO0 = 0.98 NaCl 8. An exothermic process gives off heat (warms up). An endothermic process absorbs heat (cools off). Which solutions are endothermic and which are exothermic? What is the sign of the change in enthalpy AH in each case? NaNO3 °C O slightly endothermic O- AH O+ AH O+ AH O- AH NaCH,C00 °C O exothermic Oendothermic Oexothermic + AH O slightly exothermic O- AH endothermic
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