Calorimetry and Hess' Law
Experiment 11
Calorimetry and Hess’s Law
Purpose- To determine the change in enthalpy for four reactions using calorimetry and Hess’s Law
Procedures:
A. Calibration of the Calorimeter
1. Obtain two copper cylinders and a Styrofoam cup with lid from your lab instructor. Check out a digital thermometer display from the storeroom window.
2. Set up a hot water bath using a 600mL beaker, ring stand, and Bunsen burner. Weigh the two copper cylinders to the nearest 0.01 grams. Carefully place the two copper cylinders in a 25mL test tube. Place the test tube in the hot water bath, and let the bath come to a boil while proceeding with the next step.
3. Weight the clean, dry Styrofoam cup to the nearest 0.01 g. Add 60 mL of distilled water to the cup, and reweigh the cup and water to the nearest 0.01 g. Place the cup in 400mL beaker for stability.
4. Using the digital thermometer record the temperature of the water in the cup every 30s for 4 minutes. Keep the lid on the cup, and keep the cup away from the hot water bath.
5. After the water has boiled for at least 10 minutes, record the temperature of the hot water bath using -20C to 100C thermometer. Carefully remove the test tube containing the copper cylinders from the hot water bath. Quickly dry off the test tube, and dump the copper cylinders into the Styrofoam cup. Replace the lid and immediately record the temperature with the thermometer.
6. Continue to record the temperature every 30s for at least 5 minutes. Whenever the readings are being taken, occasionally swirl the water in the cup to assure uniform temperature. Stop taking readings when a constant decrease in temperature is noted for 4consecutive readings.
7. Dump out the water and return the copper cylinders to your lab instructor now.
B. Measurements of H for neutralization reaction.
8. Add 50mL of distilled water to the cup, and pipet 10mL of standardized 3.0M HCL into the water in the cup.
Calorimetry and Hess’s Law
Purpose- To determine the change in enthalpy for four reactions using calorimetry and Hess’s Law
Procedures:
A. Calibration of the Calorimeter
1. Obtain two copper cylinders and a Styrofoam cup with lid from your lab instructor. Check out a digital thermometer display from the storeroom window.
2. Set up a hot water bath using a 600mL beaker, ring stand, and Bunsen burner. Weigh the two copper cylinders to the nearest 0.01 grams. Carefully place the two copper cylinders in a 25mL test tube. Place the test tube in the hot water bath, and let the bath come to a boil while proceeding with the next step.
3. Weight the clean, dry Styrofoam cup to the nearest 0.01 g. Add 60 mL of distilled water to the cup, and reweigh the cup and water to the nearest 0.01 g. Place the cup in 400mL beaker for stability.
4. Using the digital thermometer record the temperature of the water in the cup every 30s for 4 minutes. Keep the lid on the cup, and keep the cup away from the hot water bath.
5. After the water has boiled for at least 10 minutes, record the temperature of the hot water bath using -20C to 100C thermometer. Carefully remove the test tube containing the copper cylinders from the hot water bath. Quickly dry off the test tube, and dump the copper cylinders into the Styrofoam cup. Replace the lid and immediately record the temperature with the thermometer.
6. Continue to record the temperature every 30s for at least 5 minutes. Whenever the readings are being taken, occasionally swirl the water in the cup to assure uniform temperature. Stop taking readings when a constant decrease in temperature is noted for 4consecutive readings.
7. Dump out the water and return the copper cylinders to your lab instructor now.
B. Measurements of H for neutralization reaction.
8. Add 50mL of distilled water to the cup, and pipet 10mL of standardized 3.0M HCL into the water in the cup.