材料合成化学作业 科大.docx

第二次作业第一题（答案标红）b 1. The Ellingham diagram shows values of which thermodynamic quantity as a function of temperature? a Standard electrode voltage; b Standard free energy change of reaction; c Partial pressure of gas; d Enthalpy change of reaction. a,c 2For a closed system at equilibrium at a temperature T, which of the following statements are true?a G = 0; b G = 0;c .H = TS; d .S = 0.b 3. Why are the slopes of many of the lines on the Ellingham diagram almost identical? a Most reactions involve the elimination of one mole of gas, so there is a similar standard enthalpy change of reaction. b Most reactions involve the elimination of one mole of gas, so there is a similar standard entropy change of reaction. c The activity of most of the metals is the same. d The partial pressure of the reacting gas is the same for all reactions. b 4. What thermodynamic quantity does the intercept at T=0 K for any standard free energy vs T line signify? a The approximate value of the standard entropy change; b The approximate value of the standard enthalpy change; c The equilibrium constant for the oxidation reaction; d Heat capacity of the oxide. a 5. What is the decomposition temperature (to the nearest 50 K) for Ag2O? (This question should be completed with the help of the interactive Ellingham diagram included with this TLP). a 460 K b 500 K c 540 K d 620 K c 6. What is the decomposition temperature (to the nearest 50 K) for PdO? (This question should be completed with the help of the interactive Ellingham diagram included with this TLP). a 1050 K b 1100 K c 1150 K d 1200 K a,d 7. Which of the following elements can be used to produce Cr from Cr2O3 at 1200K? (This question should be completed with the help of the interactive Ellingham diagram included with this TLP).a Mg b .Fec Cod Al 第二题请学习如何从Ellingham图中查出温度T时某金属氧化物（e.g. MO2与H2-H2O平衡体系的H2/H2O摩尔比（或P(H2)/P(H2O)的方法，并推导其理论根据。解：（1） 对于2M（s)+O2(g)=2MO2(s) 平衡常数可以表示为：(因为M和MO2都是固体）。(2)根据热力学的一些知识我们知道：在平衡状态时，因此有，所以（3） 对于2M（s)+O2(g)=2MO2(s) , 有 , 则 ： 由此我们可以得出由某个温度下的值得到O2的平衡分压。从the Ellingham diagram读的步骤：以下图为例，先随意选择一个温度T 在选定的温度点作x轴垂线，与2M（s)+O2(g)=2MO2(s)反应的-T线相交于一点A（如下图红点），然后再过原点B（0，0），即标黄的点，与A点这两个点作直线，该直线与右边O2分压的列坐标相交于一点C（标成蓝色），从这个相交点就读出了该温度下此反应的。 再把转化成，我们就从图中得到了反应平衡O2分压值。CBAT（4） 以上的推断都是对于纯O2参与而言的，金属氧化成金属氧化物的气相不一定完全是O2，比如还能是：MO2与H2-H2O平衡体系。此时， ，对式两边取对数ln，可得由此可以看出和是等价的。既然它们是等价的，那么我们就可以按照读O2分压的方法来查出温度T时某金属氧化物（e.g. MO2与H2-H2O平衡体系的P(H2)/P(H2O)。从图查P(H2)/P(