endothermicand exothermic reactions（endothermicand exothermic reactions）.doc

Endothermic and Exothermic Reactions Name________________________ 9-10-03 Many chemical reactions give off energy. Chemical reactions that release energy are called exothermic reactions. Some chemical reactions absorb energy and are called endothermic reactions. You will study one exothermic and one endothermic reaction in this experiment. In Part I, you will calibrate the temperature probes that you will use in the exothermic and endothermic reactions. In Part II, you will study the reaction between citric acid solution and baking soda. An equation for the reaction is: H3C6H5O7(aq) + 3 NaHCO3(s) → 3 CO2(g) + 3 H20(l) + Na3C6H5O7(aq) In Part III, you will study the reaction between magnesium metal and hydrochloric acid. An equation for this reaction is: Mg(s) + 2 HCl(aq) → H2(g) + MgCl2(aq) Another objective of this experiment is for you to become familiar with Logger Pro, a program you will use with nearly every experiment in this manual. In this experiment, you will use Logger Pro to collect and display data as a graph or table, analyze your experimental data values, and print a graph or data table. MATERIALS Macintosh or IBM-compatible computer citric acid, H3C6H5O7, solution Serial Box Interface or ULI NaHCO3 hydrochloric acid , HCl LoggerPro solution magnesium, Mg Vernier Temperature Probe baking soda 50-mL graduated cylinder hotplate 2, 100-mL beaker balance 250-mL beaker thermometer Styrofoam cup hot mitten PROCEDURE 1. Obtain and wear goggles. Part I Temperature Probe Calibration The temperature probes used in this experiment produce an electrical signal that changes with the temperature the probe is sensing. In order for the computer to accurately convert the electrical signal into a temperature in degrees that we can read the sensors must be “calibrated”. 2. Fill both 100-mL beakers with 75-mL of tap water. Place the one of the beakers containing tap water on the hot plate. Plug in the hot