设NA代表阿伏加德罗常数的值。下列有关叙述正确的是[ ] ①标准状况下,2.24

题型:选择题

问题:

设NA代表阿伏加德罗常数的值。下列有关叙述正确的是[ ]

①标准状况下,2.24 L水中含有的分子数为0.1NA

②23 g Na在氧气中完全燃烧失电子数为NA

③含1mol溶质的硫酸钾溶液中阴离子所带电荷数为NA

④常温常压下,32 g O2-中所含电子的数目为16NA

⑤由CO2和O2组成的混合物中共有个NA分子,其中氧原子数为2NA

⑥1mol CO2中共价键总数为2NA

A.①②⑤

B.②⑤

C.③④⑤

D.②⑥

考点:阿伏加德罗常数
题型:选择题

Brian arrived at the San Francisco airport two hours before the flight to Paris. He was wearing three shirts, a jacket, two pairs of socks, a pair of shorts, and two pairs of jeans. He was carrying one small backpack, which was very full, but he didn’t have any other luggage. Brian needed to meet a man named Tony before he checked in for his flight. He found Tony near the Air France counter. Tony gave him a round-trip ticket and a small package. 

“Give this package to Jean-Paul at the airport in Paris. He will have a sign with your name on it. I think you can find him easily, “Tony said.” You don’t have any luggage, right?”

“Only this backpack,” Brian answered. “You said I could bring one carry-on bag.”

“That’s right, one carry-on bag is fine. Have a good trip.”

“Thanks.”

Is Brian a criminal(犯罪)? Not at all. He is an air courier. And he paid only $110 for the round-trip ticket to Paris. Air couriers get cheap airline tickets because they take important packages and papers to foreign countries. Businesses sometimes need to get packages and papers to people in foreign countries by the next day. Often, the only way they can do this is to use an air-courier company. It is not cheap for a business to send a package with an air courier, but it is quick. 

Every year about 80, 000 people worldwide travel as air couriers. The number of tickets for courier travel is growing by about 10 percent a year. However, air-courier travel isn’t for everyone, But if you have very little money, can be flexible(灵活的)about your travel plans, and don’t mind wearing the same clothes for a week, it can be a great way to take a vacation!

小题1:Why was Brian wearing so many clothes for his travel?

A.Because they were the uniform for air couriers,

B.Because that made him easier to be recognized.

C.Because his backpack had no room for his clothes.

D.because he did not have any luggage with him.小题2:An air courier is a person who        

A.manages a business company in foreign countries

B.organizes international flights for tourists

C.travels around the world with cheap tickets

D.delivers papers and packages to foreign countries小题3:Businesses choose the air-courier service because      

A.it costs less

B.it is flexible

C.it saves time

D.it grows fast小题4:One of the disadvantages of traveling as an air courier is that he

A.cannot decide when and where to travel

B.cannot take any luggage with him

C.has to wear two pairs of jeans

D.saves little money from the travel小题5:The author of the text mainly

A.describes the activities of a law-breaker

B.suggests an ideal way to travel

C.argues against the air-courier travel

D.tells us about a developing business

题型:选择题

下列匹配不正确的是(  )

A.巴西--足球

B.西班牙--斗牛

C.波兰--风车

D.阿拉伯--驼队

题型:选择题

在开采过程中,露天矿场被划分为若干具体有一定高度的水平分层或有某些倾斜的分层。这种分层被称为()。

题型:选择题

消费者总是想用同样多的货币买到更多的商品。但从长远来看,物价持续下降、通货紧缩却不是我们所希望的,因为这会导致()

A.流通中的货币量减少→居民购买力下降→社会有效需求不足→生产萎缩

B.社会投资减少→生产萎缩→失业率上升→经济衰退

C.生活资料价格下降→居民购买力上升→居民消费需求增加→物价上涨

D.生产资料价格下降→企业生产成本降低→企业经济效益提高→经济过热

题型:选择题

由于重整CB-7催化剂需要控制水一氯平衡,因此它不是全氯型催化剂。

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