问题 问答题

低碳经济呼唤新能源和清洁环保能源.煤化工中常需研究不同温度下的平衡常数、投料比及热值等问题.已知:CO(g)+H2O(g)⇌H2(g)+CO2(g)△H=a kJ•mol-1的平衡常数随温度的变化如下表:

温度/℃400427700800
平衡常数9.949b0.64
(1)a______0 (填“<”或“>”).若到达平衡后升高温度,则CO的转化率将______,正反应速率______(填“增大”、“减小”或“不变”).

(2)若在427℃时进行,且CO、H2O的起始浓度均为0.01mol/L,在该条件下,CO的最大转化率为______.

(3)700℃时,向容积为2L的密闭容器中充入一定量的CO和H2O,反应过程中测定的部分数据见下表(表中t1>t2):

反应时间/minn(CO)/molH2O/mol
01.200.60
t10.80
t20.20
保持其他条件不变,起始时向容器中充入0.60molCO和1.20molH2O,到达平衡时,n(CO2)=______mol;b=______.

答案

(1)由表中数据可知,温度越高平衡常数越小,说明升高温度平衡向逆反应移动,则正反应为放热反应,故a>0,

平衡向逆反应移动,CO的转化率减小,升高温度反应速率加快,故正反应速率增大,

故答案为:>,减小,增大;

(2)到达平衡时转化率最大,令平衡时CO的浓度变化量为x,则:

                CO(g)+H2O(g)⇌H2(g)+CO2(g)

开始(mol/L):0.01    0.01     0      0

变化(mol/L):x          x       x      x

平衡(mol/L):0.01-x   0.01-x     x      x

x×x
(0.01-x)×(0.01-x)
=9,解得x=0.0075

故CO的转化率为

0.0075mol/L
0.01mol/L
×100%=75%

故答案为:75%;

(3)由表中数据可知,t1时刻,△n(CO)=1.2mol-0.8mol=0.4mol,根据方程式CO(g)+H2O(g)⇌H2(g)+CO2可知,△n(H2O)=0.4mol,故此时n(H2O)=0.6mol-0.4mol=0.2mol,t2时刻水的物质的量为0.2mol,故t1时刻反应达平衡,

             CO(g)+H2O(g)⇌H2(g)+CO2(g)

开始(mol):1.2     0.6      0      0

变化(mol):0.4     0.4      0.4    0.4

平衡(mol):0.8     0.2      0.4    0.4

故该温度下平衡常数为:

0.4×0.4
0.8×0.2
=1

起始时向容器中充入0.60molCO和1.20molH2O,到达平衡时,令二氧化碳的物质的量为y,则:

              CO(g)+H2O(g)⇌H2(g)+CO2(g)

开始(mol):0.6    1.2      0      0

变化(mol):y       y        y      y

平衡(mol):0.6-y   1.2-y     y       y

所以

y×y
(0.6-y)×(1.2-y)
=1,解得y=0.4,

故答案为:0.4,1.

填空题

Part 4


Questions 26-45


·Read the following passage and decide which answer best fits each space.
·For questions 26-45, mark one letter A, B, C or D on the Answer Sheet.
Participation (26) high school sports is not a constitutional right. (27) , it is a privilege, paid for by taxpayers, open to students who promise to (28) certain conduct requirements on and off the field. One of these promises is to (29) from using drugs. Drug use is a serious problem among high school students. Studies show that as many as 500, 000 high school students use muscle-pumping, life-destroying substances such as steroids. Many more use illegal drugs, (30) cause discipline problems and (31) the stage for lifelong (32) .
Drug testing works to (33) and identify use. That is why drug testing is required to compete in the Olympics, the National Collegiate Athletic Association and the National Football League. (34) drug testing was instituted by these organizations, use of performance- (35) drugs has been greatly reduced. We should want (36) in schools.
Indeed, many athletes (37) testing programs, and no wonder. Without testing, athletes have to choose between drug use and a competitive disadvantage (38) the field.
Those who challenge the need for drug testing may be forgetting (39) it is like be an adolescent. Peer pressure is enormous, and one of the few effective counter-weights is the fear of being caught. More importantly, once drug use is (40) , a school can (41) to the student before he or she gets addicted or arrested.
For 25 years, public schools (42) by federal judges and civil libertarians, with results everyone can see. It is time (43) decisions on how to run public schools locally (44) officials. There is nothing unconstitutional about asking those who gain the advantages of school-sponsored athletics to contribute to the safety of other players, the integrity of the game and their own well-being. The Supreme Court should leave these programs (45) .

A.nothing more

B.nothing less

C.something less

D.something more

名词解释