Analytical Chem istry - DePauw University

382 Analytical Chemistry 2.0thermogravimetry. Figure 8.10 shows a typical thermogram in whicheach change in mass—each “step” in the thermogram—represents the lossof a volatile product. As shown in Example 8.4, we can use a thermogramto identify a compound’s decomposition reactions.Example 8.4The thermogram in Figure 8.10 shows the mass of a sample of calciumoxalate monohydrate, CaC 2 O 4 •H 2 O, as a function of temperature. Theoriginal sample weighing 17.61 mg was heated from room temperature to1000 o C at a rate of 20 o C per minute. For each step in the thermogram,identify the volatilization product and the solid residue that remains.So l u t i o nFrom 100–250 o C the sample loses 17.61 mg – 15.44 mg, or 2.17 mg,which is217 . mg100 12.%317.61mg × =of the sample’s original mass. In terms of CaC 2 O 4 •H 2 O, this correspondsto a loss of0. 123× 146. 11 g/mol=18.0 g/mol1817.61 mgCaC 2 O 4 •H 2 O1615.44 mgWeight (mg)141212.06 mg1086.76 mg60 200 400 600 800 1000Temperature (°C)Figure 8.10 Thermogram for CaC 2 O 4 •H 2 O obtained by heating a sample from roomtemperature to 1000 o C at a rate of 20 o C/min. Each change in mass results fromthe loss of a volatile product. The sample’s initial mass and its mass after each lossare shown by the dotted lines. See Example 8.4 for information on interpreting thisthermogram.