Lab 10 Purpose To demonstrate how to measure the energy changes associated with various neutralization reactions, and how to measure the heat capacity of a calorimeter. Acids and Bases Acid: donates H+ ions to the aqueous solution in which it is dissolved Base: donates OH- ions to the aqueous solution or accepts H+ ions from the aqueous solution in which it is dissolved Strong acid: dissociates completely in aqueous solution Strong base: dissociates completely in aqueous solution Neutralization Reactions Strong acids and strong bases react to produce a salt and water; a solution with an overall pH of 7 under ideal conditions (neutralization reaction): HCl(aq) + KOH(aq) KCl(aq) + H2O(l) + heat Neutralization reactions are exothermic, thus liberating heat to the surroundings. Calorimetry Calorimeters measure the heat associated with a chemical reaction. We have to account for the heat transferred from the solution to the calorimeter so we can add it back in. For this reason we perform a calibration on the calorimeter prior to running the experiment on the acid / base reaction. Calorimetry Heat (q) is the transfer of energy between two objects; always from hot to cold. The amount of heat transferred depends on the mass of the object. Temperature reflects the random motion of particles in an object and is independent of mass. You will be working with both heat and temperature today. Procedure Calibrate your thermistor. Hot water bath Room temperature water bath Ice water bath Calibrate your calorimeter to find CCAL. Room temperature water Hot water Determine the energy transfer involved with your neutralization reaction. Strong acid Strong base Safety Concerns Reagents: HNO3 (1 N) / HCl (0.2 N) NaOH / KOH Eye Contact: Irritating, burns, permanent eye damage, tearing, redness, pain, impaired vision, blindness Skin Contact: Irritating, redness, pain, soreness, severe skin burns, ulcers, stains, destruction, scaling, and blistering Inhalation: Breathing difficulties, pneumonia, pulmonary edema, coughing, choking, irritation of nose, throat, and respiratory tract, burns, and death Ingestion: Pain and burns of the mouth, throat, esophagus and gastrointestinal tract. Corrosive to mucous membranes, perforation of the esophagus and stomach, abdominal pain, nausea, vomiting, abnormal sensations of hands and feet, and general gastro-intestinal upset. Waste Dispose waste in the appropriate waste receptacles. • Acidic and basic solutions / waste need to be disposed in the acid/base waste container in the fume hood. • Solutions with a pH between 6 and 8 can be disposed down the drain. Lab 11 Reminder Lab 11 is next.