问题 问答题

800K时将1mol CO和1mol H2O(g)充入体积为1L的固定容积的反应器中,在某条件下达到化学平衡状态:CO(g)+H2O(g)⇌CO2 (g)+H2 (g),此时有

2
3
的CO转化为CO2

(1)该平衡混合物中CO2的体积分数为______

(2)写出该反应的化学平衡常数表达式______,并计算出平衡常数为______

(3)若使平衡向正方向移动,则下列说法中正确的是______(填序号)

①生成物的物质的量一定增加②生成物的体积分数一定增加:③反应物的转化率一定增大;④反应物的浓度一定降低;⑤正反应速率一定大于逆反应速率;⑥一定使用了催化剂.

(4)在相同条件下,若向容器中充入1mol CO2、1mol H2和1mol H2O,则达到平衡时与(1)中平衡相比较,平衡应向______(填“正反应方向”、“逆反应方向”或“不移动”),此时平衡混合物中CO2的体积分数为______(提示:3的平方根为1.732)

答案

利用三段式法求平衡时各组分个浓度,

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

起始(mol):1             1                  0               0

转化(mol):

2
3
             
2
3
                 
2
3
              
2
3

平衡(mol):1-

2
3
=
1
3
         1-
2
3
=
1
3
           
2
3
              
2
3

 (1)反应前后气体的体积不变,所以平衡时,混合气体的总的物质的量为1mol+1mol=2mol,

所以平衡混合物中CO2的体积分数为

2
3
mol
2mol
=
1
3

故答案为:

1
3

(2)化学平衡常数=生成物平衡浓度系数次方之积与反应物平衡浓度系数次方之积的比,

故该反应的平衡常数表达式k=

c(H2)c(CO2)
c(CO)c(H2O)
,反应在同一容器内进行,体积相同,方程式中各物质的化学计量数都是1,所以在计算中均可用物质的量数值代替浓度数值,所以k=
c(H2)c(CO2)
c(CO)c(H2O)
=
2
3
×
2
3
1
3
×
1
3
=4.

故答案为:k=

c(H2)c(CO2)
c(CO)c(H2O)
;=4.

(3)平衡向向正方向移动,

①不论改变何条件,平衡向向正方向移动,生成物的物质的量一定增加,故①正确;

②对于多种气体参与反应,反应前后气体的体积不变的反应,并向其中大量加入一种反应物,而使平衡正向移动.生成物的物质的量增加,但百分含量完全可以减小,因为总量多了,故②错误;

③多种物质参加反应,增加一种反应物的浓度,平衡向向正方向移动,提高其它反应物的转化率,自身转化率降低,故③错误;

④多种物质参加反应,增加一种反应物的浓度,平衡向向正方向移动,其它反应物的浓度降低,自身浓度增大,故④错误;

⑤平衡向向正方向移动,正反应速率一定大于逆反应速率,故⑤正确;

⑥使用催化剂不能改变平衡移动,故⑥错误.

故选:①⑤

(4)充入1mol CO2、lmol H2和1mol H2O,反应向逆反应进行建立平衡,等效为(1)中平衡后,再加1molH2O(g),平衡向正反应移动;

令参加反应的H2物质的量为nmol,

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

起始(mol):0         1                 1              1

转化(mol):n         n                 n              n

平衡(mol):n        1+n               1-n            1-n

所以

(1-n)(1-n)
n(1+n)
=4,解得n=0.154

反应前后气体的体积不变,所以平衡时,混合气体的总的物质的量为1mol+1mol+1mol=3mol,

平衡混合物中CO2的体积分数为

1mol-0.154mol
3mol
×100%=28.2%

故答案为:28.2%

完形填空
One day, a kind woman happened to say something that hurt her best friend of many years. She 1  immediately and would do anything to take the words back. What she said hurt the friend so   2  that this good woman was herself hurt for the   3  she caused. In an effort to undo what she had done, she went to an older, wiser woman in the village, explained her  4 , and asked for advice.
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小题2:
A.deeply B.slightly C.littleD.straight
小题3:
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A.appealedB.returnedC.wavedD.nodded
小题14:
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小题18:
A.words B.friends C.promisesD.expectations
小题19:
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小题20:
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单项选择题