Thermochemistry Formal Lab

Purpose: The objective of this lab is to observe reactions that characterize the laws of thermo chemistry quantitatively. Hypothesis: For Part I, the change in heat for HCl will be greater than that of HC2H3O2. Procedure: Part I: Heat of Neutralization 1. Dry the Styrofoam cup and thermometer with paper towel. Measure 25mL of 1.0M NaOH and add it to the Styrofoam cup. 2. Place the lid on the Styrofoam cup. Measure 25mL of HCl into a clean graduated cylinder. 3. Measure the temperature of the acid. Rinse the thermometer with water and wipe dry. 4. Insert the thermometer into the Styrofoam cup and measure the temperature of the NaOH solution. The temperature of the NaOH and the HCl should be very similar. 5. Record the temperature of the NaOH solution. 6. Lift the lid carefully and add the HCl all at once. Be careful not to splash any on the upper side of the cup. Swirl the solution (gently) and observe the temperature for the next 3 minutes. 7. Record the highest temperature change. 8. Repeat for 1.0 M HC2H3O2 and 1.0 M NaOH. Part II: ΔE, ΔH, q, w 1. Turn on the hot plate. 2. Mass an empty 250mL beaker. Add 10mL of water and mass the beaker and the water. This is System A.

3. Mass an empty 250mL beaker. Add 10mL of water and mass the beaker and the water. This is System B. 4. Add 3 to 4 boiling chips to each beaker. 5. Place both beakers on the hot plate. 6. When System A begins to boil, quickly stir and record the temperature of the 150mL of water. 7. As System A is nearly completely boiled away, watch it carefully ad as the beaker sweeps to dryness, stir and record the temperature of the 150mL of water. 8. Immediately use the beaker tongs to remove the empty beaker from the hot plate. 9. Remove the other beaker and turn off the hot plate. 10. Read the thermometer. Part III: Hess’s Law and the Heat of Formation 1. Set up the Styrofoam calorimeter. Cut off the rim of one cup with scissors and nestle the cup upside down inside the other one. Remove the cup and make a small hole in the bottom for the thermometer. 2. Neutralization: Place 50mL of 1.5 M NH3 in the bottom of the calorimeter and the same amount of 1.5 M HCl in a beaker. Record the temperature of each solution. Lift up the top of the thermo cup and add all the acid. Replace the top, stir gently with the thermometer and record the highest temperature obtained within the next minute. 3. Dissolving: Calculate the mass of the NH4Cl that must be added to 100mL of distilled water to get NH4Cl of the same concentration as the final solution in step 2. Put 100mL of the water in the cup and read the

temperature. Add the correct amount of NH4Cl, stir and determine the final the final extreme temperature of the solution when the entire solid is dissolved. 4. Repeat the neutralization and dissolving set by changing to 1.5 M H2SO4 and (NH4)2SO4. In this case, adjust the relative volumes of NH3 and H2SO4 to allow for the double equivalence of the acid. Data Table: Part I: Volume of HCl (mL) Volume of NaOH(mL) Initial Temperature of HCl (oC) Initial Temperature of NaOH (oC) Final Temperature (oC) Temperature Change (oC) Part II: Mass of Beaker w/o 10 mL H2O (g) Mass of Beaker w/o 150mL H2O (g) Mass of Beaker w/ 10 mL H2O (g) Mass of Beaker w/o 150 mL H2O (g) Temperature of 150 mL beaker after 10mL H20 boiling (oC) Temperature of 150 mL beaker after 10mL H20

25.0 01 25.0 01 24.2 1 24.0 1 30.0 1

±.

Volume of HC2H3O2 (mL)

±.

Volume of NaOH(mL)

±.

Initial Temperature of HC2H3O2 (oC) Initial Temperature of NaOH (oC) Final Temperature (oC)

±. ±.

86.537 ± . 001 106.701 ± . 001 96.537 ± . 001 256.701 ± . 001 35.0 ± .01

84.0 ± .01

25.0 01 25.0 01 24.5 1 24.0 1 30.0 1

±. ±. ±. ±. ±.

evaporated (oC)