问题 选择题

(09青岛)在氯化铜和氯化亚铁的混合溶液中加入一定量的镁粉,充分反应后过滤,向滤出的固体中滴加稀盐酸,没有气泡产生。下列判断正确的是(    )

A.滤出的固体中一定含有铜,可能含有铁和镁

B.滤出的固体一定含有铜,一定不含铁和镁

C.滤液中一定含有氯化镁和氯化亚铁,可能含有氯化铜

D.滤液中一定含有氯化镁、氯化亚铁、氯化铜

答案

BC

根据金属活动顺序表知镁比铁活泼,铁比铜活泼,所以加入镁粉,首先镁粉和氯化铜溶液反应,置换出单质铜,如果镁粉足量可以再继续和氯化亚铁反应置换出铁,向滤出的固体中滴加稀盐酸,有少量气泡产生,说明固体中含有和稀盐酸反应的金属.

A、因为滤出的固体能和盐酸反应,说明含有能和酸反应的活泼金属,但不能确定和盐酸反应的是铁还是铁和镁的混合物,故固体中一定含有Cu、Fe、Mg的说法错误.

B、因为为滤出的固体能和盐酸反应,但不能确定镁是否有剩余,故此项说法正确.

C、根据金属活动性顺序和加入盐酸后的现象,滤液中一定含有MgCl2,可能含有FeCl2,说法正确,所以C正确.

D、滤液中一定没有CuCl2,因为固体中有能和盐酸反应的金属,说明氯化铜中的铜全部被置换出来了,所以D不正确.

故选BC

阅读理解

You may think that sailing is a difficult sport, but it is really not hard to learn it.You do not need to be strong.But you need to be quick.And you need to understand a few basic rules about the wind.

First, you must ask yourself, “Where is the wind coming from? Is it coming from ahead or behind or from the side?” You must think about this all the time on the boat.The wind direction tells you what to do with the sail.

Let's start with the wind blowing from behind.This means the wind and the boat are going in the same direction.Then you must always keep the sail outside the boat.It should be at a 90° angle (角度) to the boat.Then it will catch the wind best.

If the wind is blowing from the side, it is blowing across the boat.In this case, you must keep the sail half way outside the boat.It should be at a 45° angle to the boat.It needs to be out far enough to catch the wind, but it shouldn't flap (摆动).It shouldn't look like a flag on a flagpole.If it is flapping, it is probably out too far, and the boat will slow down.

Sailing against the wind is not possible.If you try, the sail will flap and the boat will stop.You may want to go in that direction.It is possible, but you can't go in a straight line.You must go first in one direction and then in another.This is called tacking.When you are tacking, you must always keep the sail inside the boat.

小题1:What should you consider first while sailing?

A.Sailors' strength.

B.Wave levels.

C.Size of sails.

D.Wind directions.小题2:What does the word “It” underlined in Paragraph 4 refer to?

A.The boat.

B.The sail.

C.The wind.

D.The angle.小题3:What do you have to do when sailing against the wind?

A.Move in a straight line.

B.Allow the sail to flap.

C.Lower the sail.

D.Tack the boat.小题4:Where can you probably find the text?

A.In a popular magazine.

B.In a tourist guidebook.

C.In a physics textbook.

D.In an official report.

单项选择题