Chemland Simulations        

 

Calorimetry

Calorimetry is a technique used to measure the amount of heat evolved from a chemical reaction performed in a bomb calorimeter (or combustion calorimeter).  A combustible sample is placed into a sample dish that is encased in a "bomb," a cylindrical container with heavy steel ends and walls.  The bomb is then placed in a thermally insulated water-filled container.  The sample of interest is ignited, usually by a spark, and the heat generated warms the bomb, which in turn warms the water.  Because heat transferred from the system (oxygen and compound) equals the heat transferred into the surroundings (bomb and water), measuring the temperature change of the water allows an accurate measurement of the heat released during the combustion reaction.  From the law of energy conservation,

Heat transferred from system = heat transferred into the surroundings
Heat evolved by the reaction = heat absorbed by water and bomb
qreaction = -(qwater + qbomb)

where q is the standard variable for heat.  Note that the heat of the reaction is negative implying that the reaction is exothermic.

This module simulates the use of a bomb calorimeter; the temperature change is calculated for the combustion of nine different compounds and displayed graphically.  The nine compounds and their molecular masses (in g/mol) are listed below:
Benzoic acid C7H6O2 122.1
Naphalene C10H8 128.2
m-Toluic acid C8H8O2 136.2
Trinitrotoluene C6H3N3O6 227.1
Sucrose C12H22O11 342.3
Lactose C12H22O11 342.3
Citric acid C6H8O7 192.1
Hydrazine N2H4 32.05

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INSTRUCTIONS:
 

  1. Select the compound to use in the calorimeter by clicking on the drop-down Compound menu and then clicking on the compound.
  2. Select the amount of compound by adjusting the Milligrams Compound scroll bar, which adjusts the amount between 0 mg and 500 mg.
  3. Select the amount of water in the calorimeter by adjusting the Grams Water in Calorimeter scroll bar, which adjusts the amount between 600 g and 1000 g.
  4. Click on the Ignite Box to start the experiment. After the initial reaction, heat is transferred to the water, which heats up over the period of a few minutes until reaching thermal equilibrium with the sample.  Note that the overall temperature change is shown numerically as well as graphically (temperature in degree Celsius vs. time in minutes).
  5. Repeat the above steps to start a new experiment.