Calorimetry
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Calorimetry For Chemistry 332
by Sepcot and El Norbo
Calorimetry: The process of determining the heat of a reaction by measuring the change in temperature in known liquids.
Equation to know:
q = m * c * DT
q: Heat of reaction (Joules or calories)
m: mass of known substance (grams)
c: specific heat (Joules per gram celsius or calories per gram celsius )
DT: change in temperature (celsius)
Common Types of Calorimeters:
1. Coffee-cup calorimeter
Two Styrofoam coffee cups are placed one inside the other and covered with a lid. The exothermic reaction occurs in the aqueous solution in the innermost container, and the cups provide enough insulation so that the heat is confined to the solution. The change in temperature of the reacting solution can be measured reasonably well with a standard laboratory thermometer.
2. Bomb calorimeter
Also known as a combustion calorimeter, a combustible sample is burned in pure oxygen in a steel "bomb." The heat generated by the reaction warms the bomb and the water surrounding it. By measuring the temperature increase, the heat evolved by the reaction can be determined. Click here for diagram of a bomb calorimeter.
Principles behind calorimetry:
All the heat evolved in the reaction is kept within the boundaries of the calorimeter. While preventing heat loss, the change in temperature is accurate to measurements and a true value of q is found. When heat is lost in a reaction to the surroundings, the value for change in temperature is too low thus resulting in a value of q which is also too low.