Immediately rinse affected areas with water for at least 15 minutes. Neutralize any spilled hydrochloric acid (HCl) with sodium bicarbonate (NaHCO 3 ) and any spilled sodium hydroxide (NaOH) with vinegar: neutralized mixtures can be rinsed down the sink. WASTE COLLECTION All solutions obtained from neutralization may be disposed down the drain. EXPERIMENTAL PROCEDURE Materials Preparation. Working in pairs, obtain four Styrofoam cups (2 cups per calorimeter) and two thermometers. Since each 2-cup calorimeter is slightly different and the calibrations of the thermometers may also be slightly different, it is important to use the same calorimeter and thermometer pairs throughout the experiment. Label one calorimeter with its thermometer as “A” and the other as “B”. Whenever you are using the calorimeters, place them gently inside a 250 mL beaker. This will help prevent them from tipping over and will also provide some additional isolation from air currents. Part A: Determining the Calorimeter Constant. When you run a reaction in aqueous solution in a calorimeter, some of the heat produced or consumed goes to change the temperature of the water and some of it goes to change the temperature of the calorimeter itself (the Styrofoam cups/thermometer). Therefore, the heat capacity of the calorimeter (its “calorimeter constant”) must be determined in a separate experiment. To begin, compare the calibration of the two thermometers by immersing both thermometers in the same beaker of tap water for 1 minute and recording the readings of each. If they are different, apply the necessary correction to all future readings. Put about 75 mL of distilled water into a 125 mL Erlenmeyer flask and heat it on a hot plate until it is 15-20°C above room temperature. Using a 50 mL graduated cylinder, transfer 50.0 mL of the heated distilled water into calorimeter A and 50.0 mL of room temperature distilled water into calorimeter B. Place the lids on both calorimeters and begin recording the temperatures of both calorimeters at 1 minute intervals. The warm water may cool slightly during this time because the thermal insulation is imperfect. After 4 minutes, quickly remove the lids from both calorimeters, pour the cold water from calorimeter B into calorimeter A, replace the lid, and continue taking temperature readings for the next three minutes. After your measurements are complete you may pour the water in the calorimeters down the drain.
Experiment#10 – Enthalpy & Hess’s Law 10 – 3 Part B: Enthalpy of Neutralization of Aqueous HCl and NaOH. Use a graduated cylinder to measure 50.0 mL of 1.0 M hydrochloric acid into calorimeter A, and 50.0 mL of 1.0 M sodium hydroxide into calorimeter B. With the lids and thermometers in place, read the temperature of each solution at 1-minute intervals for 3 minutes. Then quickly pour the sodium hydroxide solution into calorimeter A, stir thoroughly, and continue reading the temperature for another 5 minutes at 1-minute intervals. Pour the solution in the calorimeter into a large beaker to combine with other parts and neutralize. Also, rinse any pipets you used with water and toss in the “Used Plastic Pipets” container.
You've reached the end of your free preview.
Want to read all 6 pages?