The Ellingham Diagram: How to Use It in Heat-Treat-Process Atmosphere Troubleshooting
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1 MSE 2104 Thermodynamics of Materials II Practice Questions Use Ellingham Diagram (oxide) to answer the following questions: 1. What are the most and least stable metals at room temperature according to the Ellingham diagram? 2. What are the most and least stable oxides at 1400 o C according to the Ellingham diagram? 3. Why are the slopes of many of the lines on the Ellingham diagram almost identical? What are the exceptions? 4. What is the best reducing element at very high temperature (>2000 o C)? 5. Which metal oxides can CO reduce at all temperatures? 6. What is the oxygen partial pressure that is in equilibrium with Ti and TiO2 at 1500 o C? 7. What is the highest oxygen partial pressure that is in equilibrium with Mg at room temperature? 8. What is the lowest CO/CO2 pressure ratio that is in equilibrium with Ca at 1400 o C 9. Which elements can reduce Cr2O3 to Cr at 500 o C? 10. Which oxides can Co reduce at 1000 o C? 11. A smelting furnace is run at 1800 °C and 10 -14 atm partial oxygen pressure to reduce Cr2O3. Engineer in charge of production wants to reduce the temperature to cut electrical costs. How many degrees should furnace temperature be lowered while keeping oxygen pressure constant? 12. What should the temperature of a furnace to reduce Cu2O by solid carbon (C + O2 = 2CO) be set minimally? How does the reaction quotient K for the overall reduction reaction with increasing temperature? 13. Is Mn stable at an oxygen partial pressure of 10 -22 atm and 800 °C? If not, what should be done to obtain Mn at this condition? 14. Will the reaction 2Cu(l) + ½ O2(g) = Cu2O(s) go spontaneously to the right or to the left at 1500 o C when oxygen pressure is 1 atm? 15. At what partial oxygen pressure will above reaction spontaneously go in the other direction? 16. Pure iron and oxygen react accordingly to form FeO : 2Fe(s) + O ଶ (g) → 2FeO (s) a. Determine the entropy change of the reaction b. Determine the free energy change of the reaction as a function of temperature
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MSE 2104 Thermodynamics of Materials II
Practice Questions
Use Ellingham Diagram (oxide) to answer the following questions:
1. What are the most and least stable metals at room temperature according to the Ellingham
diagram?
2. What are the most and least stable oxides at 1400 oC according to the Ellingham diagram?
3. Why are the slopes of many of the lines on the Ellingham diagram almost identical? What are
the exceptions?
4. What is the best reducing element at very high temperature (>2000 oC)?
5. Which metal oxides can CO reduce at all temperatures?
6. What is the oxygen partial pressure that is in equilibrium with Ti and TiO2 at 1500oC?
7. What is the highest oxygen partial pressure that is in equilibrium with Mg at room temperature?
8. What is the lowest CO/CO2 pressure ratio that is in equilibrium with Ca at 1400 oC
9. Which elements can reduce Cr2O3 to Cr at 500 oC?
10. Which oxides can Co reduce at 1000 oC?
11. A smelting furnace is run at 1800 °C and 10-14 atm partial oxygen pressure to reduce Cr2O3.
Engineer in charge of production wants to reduce the temperature to cut electrical costs. How
many degrees should furnace temperature be lowered while keeping oxygen pressure constant?
12. What should the temperature of a furnace to reduce Cu2O by solid carbon (C + O2 = 2CO) be set
minimally? How does the reaction quotient K for the overall reduction reaction with increasing
temperature?
13. Is Mn stable at an oxygen partial pressure of 10-22 atm and 800 °C? If not, what should be done
to obtain Mn at this condition?
14. Will the reaction
2Cu(l) + ½ O2(g) = Cu2O(s)
go spontaneously to the right or to the left at 1500 oC when oxygen pressure is 1 atm?
15. At what partial oxygen pressure will above reaction spontaneously go in the other direction?
16. Pure iron and oxygen react accordingly to form FeO :
2Fe(s) + O (g) → 2FeO (s)
a. Determine the entropy change of the reaction
b. Determine the free energy change of the reaction as a function of temperature
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c. What will be free energy and the direction of the reaction when the system is left in a
furnace at 1560 oC with a large amount of Mn ?
17. Could C(s) be used as reducing agent to reduce Al2O3(s) to produce Al(l) at 900oC?
18. What is the standard Gibbs energy change ( at 1200oC) for the reaction
4/3 Cr(s) + O2(g) =2/3 Cr2O3 (s)
DOÇ.DR. EMRE YALAMAÇ
