Question

CHMISILL: THERMOCHEMISTRY 15 Name Partner Lab Report 1 Data Sheet for Citric Acid + Baking Soda Calorimetry RECORD TEMPERATURES TO THE THERMOMETER'S FULL AVAILABLE PRECISION time (s) T(°C) time () T(°C) time (s) T(°C) 20 10 90 165 150 105 180 21200 2 135 - 195 2107 Minimum or maximum temperature, T: (°C) -1°C Initial temperature, (°C) 21°C Temperature change, AT (°C)=T:-1, -22°C 1. Is the reaction you studied exothermic or endothermic? Explain your reasoning. Endothermic because it abscubina 2. Would A Hon have a positive or a negative sign? Explain your choice. If T 1 Exo Tft Land

Answer 1

1. As can be seen from the temperature data, the temperature of the calorimeter is dropping with time. Hence it is well understood that the reaction absorbing heat from the surrounding thus dropping its temperature. Hence the reaction is endothermic

2. ΔHrxn means the change in enthalpy of reaction. In other words, when a reaction takes place, its enthalpy either changes positively or negatively. In endothermic reactions, this change is positive, because the reaction system tends to absorb heat from the surrounding hence the enthalpy after reaction tends to increase and thus will have positive sign.