Calorimetry

CALORIMETRY

K.A. MARQUEZ

DEPARTMENT OF FOOD SCIENCE AND NUTRITION, COLLEGE OF HOME ECONOMICS

UNIVERSITY OF THE PHILIPPINES, DILIMAN QUEZON CITY, PHILIPPINES

DATE PERFORMED: JUNE 21,2013

INSTRUCTOR’S NAME: CHARMINE ALCANTARA

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INTRODUCTION

The universe is composed of the system, the subject or focus of the study, and the surroundings defined as all the other parts of the universe outside the system. Three types of system are as follows: open system where energy and matter can move in and/or out freely, closed system where only energy can move in and/or out freely, and isolated system where both matter and energy are confined. As said in the 1st Law of Thermodynamics, energy in the universe is constant therefore all heat gained/released by the system will be used to cool/heat the surroundings:

qsystem = -qsurroundings (1)

Transfer of energy can only be through heat and work as shown in the equation,

⍙E = q + w (2)

where q is heat and w is work.

Calorimetry is a technique or process used to measure the heat, denoted as q, absorbed or evolved in a chemical reaction. The device used in the said process is called a calorimeter. The two kinds of calorimeter are bomb calorimeter, which works for constant volume (⍙V=0), and coffee-cup calorimeter, for reactions under constant pressure (⍙P=0). An isolated coffee-cup calorimeter will be used in the experiment.

The heat measured from the reaction under constant pressure is called enthalpy, H. Change in enthalpy, ⍙H, describes a reaction as either exothermic or endothermic reaction. In an exothermic reaction, the energy which is in the form of heat transfers from the system to the surroundings and accounts to a negative value for ⍙H. Meanwhile, energy transfers to the system from the surroundings in an endothermic reaction giving us a positive ⍙H in the equation,...