问题 问答题

常温下,将28.9g氯化钠和碳酸钠的白色固体混合物溶于145g水中,向其中加入30.5g稀盐酸,恰好完全反应,可得到200g不饱和溶液.求反应后所得溶液中溶质的质量分数?______.

答案

设混合物中Na2CO3的质量为x,反应后生成NaCl的质量为y.

根据题意,反应后生成CO2的质量为:28.9g+145g+30.5g-200g=4.4g

Na2CO3+2HCl=2NaCl+H2O+CO2

106          117     44

x             y     4.4g

106
x
=
117
y
=
44
4.4g

x=10.6g;y=11.7g

反应后所得溶液中溶质的质量分数为:

11.7+(28.9-10.6)
200
×100%=15%

答:反应后所得溶液中溶质的质量分数为15%.

阅读理解

阅读表达。阅读下面的短文,并根据短文后面的要求答题。(请注意问题后的字数要求)

     For years children in the industrial areas of Europe and America seldom left their smoky cities to see the

beauties of the countryside. Not that the woods and fields were always far away, but they were too far from

the city to permit people to make a round trip between morning and nightfall. What's more, factory workers

did not have enoug money to send their children on country holidays away from home.

     In 1907 a young German schoolmaster had an idea which changed this state of affairs. He decided to turn

his little schoolhouse into a domitory for the summer holidays. Anyone who bmught his sleeping bag and

cooking equipment along could stay there for a very smaU amount of money. The idea was a success. A few

years later the schoolhouse was far too small to hold so many young people who wanted to stay there. So, a

dormitory was set up in an old caste nearby. This was the first Youth Hostel.

     Today young students and workers of every country can meet in the hostels and get to know each other.

Some spend a week or more in the same hostel, seeing the surrounding sights and meeting the people of the

area. Other youths go on foot or by bicycle from place to place, spending a night or two in one hostel, then

going to the next.

     Sometimes an infomal program will be organized after the meal, with dances, songs, or short talks followed

by a question period. One can _____ about other places, just by meeting people who come from these places.

For this reason, a few weeks spent "hostelling" can be just as useful a part of one's education as classes in

school.

1. Translate the underlined sentence in paragraph l into Chinese.

    _______________________________________________________________________________________

2. What does paragraph 2 mainly tell us? (Please answer within 10 words)

    _______________________________________________________________________________________

3. Which sentence in the text is the closest in meaning to the following one? Some youths stay in a hostel for 

    several days, during which period they go sightseeing and visit the local people.

    _______________________________________________________________________________________

4. Fill in the blank in the 4th pamgraph with proper words to complete the sentence. (P1ease answer within 7

    words)

    _______________________________________________________________________________________

5. List 3 of the advantages of hostelling according to the text. (Please answer within 15 words)

    _______________________________________________________________________________________

单项选择题 B1型题