9. The following figure shows combined thermogravimetric analysis (TGA) thermal
ID: 3349662 • Letter: 9
Question
9. The following figure shows combined thermogravimetric analysis (TGA) thermal analysis (DTA) data for heating up a solid in air to 1200'C at 10' isothermally at 1200'C for 20 minutes, then cooling to room temperature at 10'C min different ana, holding 7 :17 05 50.2 50 05 421 + 49 6 49.4 -15 200 400 600 800 1000 1200 Tempic (a) There are 3 phase changes that occur during this process -2 during heating and 1 during cooling. At what temperatures do these 3 phase changes occur, are they associated with mass gain or loss, and are they exothermic or endothermic? (b) Based on these data, is the overall process reversible or irreversible? 10. Thermogravimetric data was collected for the oxidation of SrMnOssty to form Sr2Mn0s by heating to 600°C in pure 02(g) at a ramp rate of 5°C min" then holding isothermally for 20 minutes. Given that the initial mass was 60.55 mg and the final mass was 62.11 mg, calculate x. 13] There are [50] total marks available for this worksheet. Grade will be given as a percentage.Explanation / Answer
(a) There are three phase changes occuring in the graph. Two phase changes while heating and one phase change while cooling.
The two phase changes occured in heating are:
1. Occurs at 600 degree centigrades and it losses mass.
2. Occurs at 800 degree centigrades and here also it losses mass.
Third phase change occurs while cooling and occurs at 700 degree centigrade. In this process the solid gains its mass.
Exothermic is a process that releases energy in the form of heat and endothermic processes absorbs energy.
Here the process of heating is nothing but exothermic as the mass is reduced and converted to the heat form and the process of cooling is the endothermic processes where the solid gains mass.
(b) By observing the overall data, the process is irreversible.
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