问题 选择题

向一洁净干燥的烧杯中加入44.4gAl粉与Fe粉混合物,然后加入过量的盐酸,产生标况下气体26.88L。若将该混合物加入500mL14 mol·L-1的HNO3中(不考虑发生钝化),产生的气体(标准状况下测定)如图所示,假设HNO3的还原产物为NO与NO2,那么理论上从哪一时刻开始产生NO气体?(假设浓度小于9mol/L为稀HNO3

A.t1

B.t2

C.t3

D.t4

答案

答案:C

题目分析:由Al粉与Fe粉的混合物共44.4g,与过量盐酸反应产生标况下     气体26.88L,根据得失电子守恒可以计算出Al与Fe分别是0.4mol、0.6mol,将该混合物加入500mL14  mol·L-1的HNO3中,若金属全部生成+3价硝酸盐,则未被还原的硝酸的物质的量为3mol,被还原的硝酸的物质的量由图中的气体体积可知是2mol,所以共消耗硝酸3+2=5mol<0.5ml×14 mol·L-1=7mol,硝酸过量,固体全部溶解。设气体产物中NO与NO2的物质的量分别为x、ymol,根据得失电子守恒可得,3x+y=(0.4+0.6)×3,x+y=2,解得x=0.5,y=1.5,1.5mol×22.4L/mol=33.6L,所以理论上在t3时刻开始产生NO气体,答案选C。

考点:

完形填空

请阅读下面短文。根据短文内容从下面方框里的七个选项中,选择五个适当的句子还原到原文中,使短文意思通顺、结构完整。(每小题2分)

小题1:___________ Some people spend so much time in malls that they are called “mall rats”. Mall rats shop until they drop in at hundreds of stores under one “roof”(房顶).

小题2:_____________ They feel safe because malls have police stations or security guards(保安). Parking is usually free, and the weather inside is always fine. The newest malls have beautiful rest areas with waterfalls and large green trees.

The largest mall in the United States is the Mall of America in Minnesota. It covers(占地) 4.2 million square feet. It has 350 stores, eight night clubs, and a seven-acre(公顷) park! There is a parking space for 12,750 cars. About 750,000 people shop there every week.

The first indoor mall in the United States was built in 1965 in Edina, Minnesota. People love doing all their shopping at one place, so, more malls have been built all over the country. 小题3:__________ They shop, of course. They also eat in food houses that have food from all over the world. They see movies at theaters. 小题4:____________ Others go to malls to meet friends.

In some malls, people can see a doctor or a dentist and even attend church (做礼拜).

小题5:______________ Now people can actually live in their favorite shopping center.

A.In other words, people can do just about everything in malls.

B.How do you know people like malls?

C.Now, malls like town centers where people can do many things.

D.Americans like malls for many reasons.E. We can do many things in malls.

F. Malls are popular places for Americans to go.

G. Some people even get their daily exercise by doing the new sport of mall walking.

选择题