问题 计算题

金属铁用途广泛,高炉炼铁的总反应为:Fe2O3(s)+3CO(g)2Fe(s)+3CO2(g),请回答下列问题:

(1)一定温度下,在体积固定的密闭容器中发生上述反应,可以判断该反应已经达到平衡的是     

A.密闭容器中总压强不变

B.密闭容器中混合气体的平均摩尔质量不变

C.密闭容器中混合气体的密度不变

D.c(CO)= c(CO2)E.Fe2O3的质量不再变化

(2)一定温度下,上述反应的化学平衡常数为3.0,该温度下将4molCO、2molFe2O3、6molCO2、5molFe加入容积为2L的密闭容器中,此时反应将向      反应方向进行(填“正”或“逆”或“处于平衡状态”);反应达平衡后,若升高温度,CO与CO2的体积比增大,则正反应为      反应(填“吸热”或“放热”) 。

(3)已知:3Fe2O3(s)+CO(g)2Fe3O4(s)+CO2(g) △H="–47" kJ/mol

Fe3O4(s)+CO(g)3FeO(s)+CO2(g)   △H=" +19" kJ/mol

FeO(s)+CO(g)Fe(s)+CO2(g)      △H="–11" kJ/mol

则Fe2O3(s)+3CO(g)2Fe(s)+3CO2(g)的△H=            

(4)上述总反应在高炉中大致分为三个阶段,各阶段主要成分与温度的关系如下表:

温度 250℃ ~  600℃ ~  1000℃ ~  2000℃
主要成分      Fe2O3        Fe3O4          FeO            Fe
 

800℃时固体物质的主要成分为         ,该温度下若测得固体混合物中m(Fe)︰m(O)=105︰32,则Fe3O4被CO还原为FeO的百分率为            (设其它固体杂质中不含Fe、O元素)。

答案

(16分)

(1)BCE(3分) (2)逆(3分)  放热(2分)  (3)–25 kJ/mol (3分)  

(4)Fe3O4  FeO(2分)   80% (3分)

题目分析:(1)由高炉炼铁总反应可知,该反应是气体体积或物质的量不变的反应,则恒温恒容下气体的压强始终保持不变,所以总压强不变不能说明该反应达到平衡,故A错误;由于容器内混合气体的平均摩尔质量等于总质量与总物质的量之比,虽然物质的量保持不变,但是混合气体的质量逐渐增大,因为氧化铁变为单质铁导致固体的质量减少,所以混合气体的平均摩尔质量逐渐增大,当它保持不变时,说明该反应已达平衡,故B正确;由于容器中混合气体的密度等于总质量与容积之比,虽然容积保持不变,但是混合气体的总质量逐渐增大,则混合气体的密度逐渐增大,当它不变时,说明该反应已达平衡,故C正确;平衡时各组分的浓度都保持不变,但是平衡浓度之比不一定等于化学方程式中系数之比,故D错误;氧化铁是反应物或原料,随着反应的进行,氧化铁被消耗,其质量逐渐减小,当它的质量不再变化,说明该反应已达平衡,故E正确;(2)温度不变,该反应化学平衡常数[K=c3(CO2)/c3(CO)]不变;起始时c3(CO2)/c3(CO)=(6/2) 3/(4/2) 3=27/8>K=3.0,则此时反应必须向逆反应方向进行,使生成物浓度减小、反应物浓度增大,c3(CO2)/c3(CO)的比值才能减小为3.0,才能达到该温度下的化学平衡;由于化学平衡常数等于生成物浓度幂之积与反应物浓度幂之积的比值,则该反应的平衡常数为c(E)/[c2(A)·c(B)];升高温度,CO与CO2的体积比增大,后者说明平衡向逆反应方向移动,前者导致平衡向吸热反应方向移动,即逆反应是吸热反应,则正反应是放热反应;(3)先将四个热化学方程式依次编号为①②③④,观察已知焓变和未知焓变的热化学方程式可得:(①+②×2+③×6)/3=④,根据盖斯定律可知,④的焓变=[(–47)+(+19)×2+(–11)×6] kJ/mol /3=–25 kJ/mol;(4)依题意可知,800℃时固体物质的主要成分为Fe3O4、FeO;设固体混合物含有xmolFe3O4、ymolFeO,则n(Fe)=(3x+y)mol、n(O)=(4x+y)mol,m(Fe)=56×(3x+y)g、m(O)=16×(4x+y)g,m(Fe)/ m(O)="[" 56×(3x+y)]/[ 16×(4x+y)]=105/32,(4x+y)/ (3x+y)=112/105,x/(3x+y)=1/15,则y=15x;由于Fe3O4(s)+CO(g)3FeO(s)+CO2(g),根据系数之比等于物质的量之比可知,被CO还原为ymolFeO的Fe3O4为y/3mol或4xmol,则总的Fe3O4为(x+y/3)mol或5xmol,被还原的Fe3O4与总的Fe3O4之比为(y/3)/ (x+y/3)=(4x)/(x+4x)=4/5,4/5×100%=80%,则Fe3O4被CO还原为FeO的百分率为80%。

完形填空
Some people believe that greed and selfishness has become the basis of modern society, and we should return to the old traditions of family and community, then we will have a better life. To what extent do you agree or disagree with the above opinion?
In this fast-paced world, many values are undergoing major changes. While people traditionally prioritize caring, sharing and generosity in life and work, modern people seem to be more self-absorbed and self-concerned.
Modern people act selfishly to survive the harsh competition of life. They say that it is a jungle out there. To survive, you have to fight with whatever means that come handy. Obviously greed and selfishness go perfectly well with such ideas. In a company, employees do everything they can to get better pay and higher position, even at the cost of colleagues. We are in any way advocating(拥护)any selfish conduct. It is just that people are pressured to behave in a different way due to outside influences.
Are we happier to share with others and be generous to them? There is no fixed answer, either. Some people take great pleasure helping and giving to others while others feel happy doing the opposite. But I personally think that people should not be too selfish. Caring for others can actually encourage the development of a friendly relationship.
In conclusion, modern people appear to be more self-centered than those in the past due to strong outside pressure. However, we should encourage people to know the importance of being caring and generous and to build a friendly relationship with others.
Are modern people becoming more selfish?
Main comparisons
Contexts
小题1:_____ are changing.
In the past people put caring, sharing and generosity in the first 小题2:_____.
Nowadays, people seem to be more 小题3:_____ about themselves.
小题4:_____ are changing too.
People in the past appeared to be modest and self-effacing(谦让的).
People may strive to achieve their own小题5:_____ at the price of their coworkers.
The author’s understanding
小题6:_____ for the changes in the author’s eyes
Fierce 小题7:____ and great 小题8:______ on modern people may be responsible for the changes.
The author’s 小题9:____ towards the topic
A 小题10:____ which can benefit two sides should be established.
 
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