Heat Exchange During Chemical Reactions Ms. Pittman Mathematics & Science Center
OBJECTIVES Use a calculator based laboratory system to collect and analyze lab data Monitor temperature changes during a chemical reaction Classify the reaction as endothermic or exothermic Calculate the change in enthalpy for the reaction ( H)
Chemical Reactions
“Clues” Precipitate forms (ppt) Gas evolved Heat released or absorbed
Enthalpy From the Greek word “enthalpein”. Denoted as “H”. Represents the heat content of a substance at a given temperature and pressure. Is a state function. Cannot be measured directly. Is an extensive property.
Formula: H = H final - H initial H = q p q = C m T where C = 1 cal/g°C H = “-” for an exothermic reaction H = “+” for an endothermic reaction
Vinegar & Baking Soda
Endothermic or Exothermic? HC 2 H 3 O 2 (aq) + NaHCO 3 (s) CO 2 (g) + H 2 O (l) + NaC 2 H 3 O 2 aq)
Tide Detergent and Water
Endothermic or Exothermic?
Post Lab Discussion