问题 填空题

在2 L密闭容器中,800℃时反应2NO(g)+O2(g)2NO2(g)体系中,n(NO)随时间的变化如表:

时间/s012345
n(NO)/mol0.0200.0100.0080.0070.0070.007
 

(1)上述反应________(填“是”或“不是”)可逆反应。

(2)如图所示,表示NO2变化曲线的是______。用O2表示从0~2s内该反应的平均速率v=________。

(3)能说明该反应已达到平衡状态的是________(填序号)。

a.v(NO2)=2v(O2

b.容器内压强保持不变

c.v(NO)=2v(O2

d.容器内密度保持不变

答案

(1)是 (2)b 1.5×10-3mol·(L·s)-1 (3)bc

(1)该反应是可逆反应。

(2)由平衡体系2NO(g)+O2(g)2NO2(g)知,NO2为生成物,n(NO2)=Δn(NO)=0.020mol-0.007mol=0.013mol

c(NO2)==0.006 5mol·L-1

故表示NO2变化曲线的为b。

v(NO)==0.003mol·(L·s)-1

则v(O2)=v(NO)=0.001 5mol·(L·s)-1

(3)a项中未指明正、逆反应速率,故无法说明该反应是否达到平衡状态;由于该反应是反应前后气体体积不相等的反应,当容器内压强保持不变时,说明该反应已达到平衡状态,故b项正确;c项中已说明正、逆反应速率相等,故说明该反应已达到平衡状态;由于气体总质量不变,气体总体积也不变,因此,无论该反应是否达到平衡,容器内密度保持不变,故d项无法说明该反应是否达到平衡状态。

阅读理解

阅读短文,选择正确答案。

       Every country has its own (自己的) way of cooking. American people have their way of cooking.

       Most people in the United States like fast food, but if you think that American people don't like cooking, you

are wrong. It's true (真实的) that most Americans eat fast food for their breakfast and lunch, but they also think

cooking is interesting. Parents see the importance of teaching their children how to cook, and most Americans

say that home-cooked meals are the best.

       Americans have their own way of cooking. For example, baking (烘烤) is the most popular way of cooking

in America. Most American families have ovens (烤炉). American cooks (厨师) pay attention to (注意) the

balance of food. In planning a big meal, they try to cook meat, a few vegetables, some bread and often some

sweet food. They also like to make the meal look beautiful. There are many kinds of food of different colors, so

the meal is healthy and looks beautiful, too.

1. Most Americans _______. [ ]

A. like fast food

B. like having a picnic (野炊)

C. don't like cooking

D. cook food in the morning

2. _______ is the most popular way of cooking in the USA. [ ]

A. Cutting

B. Baking

C. Frying

D. Peeling

3. From this passage, we know _______. [ ]

A. most Americans like to eat fast food for dinner.

B. most Americans don't have breakfast or lunch.

C. most Americans have fast food for their breakfast or lunch.

D. most Americans don't eat fast food for their breakfast or lunch.

4. How does an American cook balance different kinds of food? [ ]

A. He makes the food delicious.

B. He cooks a lot of meat for a big meal.

C. He cooks a lot of vegetables for a big meal.

D. He cooks meat, vegetables, bread and sweet food for a big meal.

5. Which of the following is RIGHT according to (根据) the passage? [ ]

A. The meal looks beautiful because the food is in different colors.

B. American parents do not like to teach their children how to cook.

C. American people do not like to cook food at home.

D. Most people in the United States don't like fast food at all.

问答题 简答题