问题 填空题

下表是氯化铵在不同温度下的溶解度:

温度(℃)010203040506070
溶解度(g/100g水)29.433.337.241.445.850.455.060.2
 

(1)从表中可知:随温度升高氯化铵的溶解度       

(2)60℃时,向盛有50 g水的烧杯中加入30 g氯化铵,充分搅拌,可得到氯化铵的        (填“饱和”或“不饱和”)溶液,溶质的质量分数是          

(3)A烧杯是70℃时,溶剂为100g的氯化铵不饱和溶液,经过如下图的变化过程(在整个过程中不考虑水分的蒸发)。

Ⅰ. C烧杯溶液中溶质的质量为         g。

Ⅱ.70℃时,将A烧杯中的溶液恒温蒸发10 g溶剂后,析出a g固体,再继续恒温蒸发30g溶剂,则析出固体b克,则b克        3a 克(填“<、≤、>、≥或=”)。

Ⅲ.有关三个烧杯中溶液的说法,错误的是         (填字母序号)。

a.B烧杯中溶液是不饱和溶液

b.A、B、C烧杯中的溶液在变化过程中,溶解度一定改变

c.由60℃降温至50℃时溶液质量一定减少

d.降温至60℃时,溶液中溶质质量分数一定不变

e.降温至30℃,烧杯中一定有NH4Cl晶体析出

答案

(1)增大

(2)饱和 ,35.5%或11/31  

(3)37.2 ,> ,a、c、e

题目分析:(1)从表中可知:随温度升高氯化铵的溶解度增大;

(2)60℃时,氯化铵的溶解度为55g,即100g水中可溶解55g达到饱和,现50 g水的烧杯中加入30 g氯化铵,氯化铵只能溶解22.5g,由固体剩余,得到的是饱和溶液,溶质的质量分数为

22.5g/72.5g  ×100% =35.5% ;

(3)C烧杯溶液是饱和溶液,20℃氯化铵的溶解度为37.2g,故C烧杯溶液中溶质的质量为37.2g ;A烧杯是70℃时,溶剂为100g的氯化铵不饱和溶液,开始10 g溶剂后,析出a g固体后得到的是饱和溶液,故b克>3a 克;B烧杯中溶液中无晶体析出,可能是不饱和溶液,也可能恰好饱和;溶解度由温度有关,温度变,则溶解度变;由60℃降温至50℃时若溶液仍是不饱和溶液,则溶液质量不变;溶液中溶质质量分数由溶质和溶剂的质量决定,溶质和溶剂的质量不变,则溶质质量分数一定不变;降温至30℃,若达到饱和,则由晶体析出,若不饱和,则无晶体析出。

单项选择题
阅读理解

No one can avoid being influenced by advertisements. Much as we may pride ourselves on our good taste, we are no longer free to choose the things we want, for advertising exerts a subtle influence on us. In their efforts to persuade us to buy this or that product, advertisers have made a close study of human nature and have classified all our little weaknesses.

Advertisers discovered years ago that all of us love to get something for nothing. An advertisement which begins with the magic word FREE can rarely go wrong. These days, advertisers not only offer free samples, but free cars, free houses, and free trips round the world as well. They devise hundreds of competitions which will enable us to win huge sums of money. Radio and television have made it possible for advertisers to capture the attention of millions of people in this way.

During a radio programme, a company of biscuit manufacturers once asked listeners to bake biscuits and send them to their factory. They offered to pay $10 a pound for the biggest biscuit baked by a listener. The response to this competition was tremendous. Before long, biscuits of all shapes and sizes began arriving at the factory. One lady brought in a biscuit on a wheelbarrow. It weighed nearly 500 pounds. A little later, a man came along with a biscuit which occupied the whole of his car. All the biscuits that were sent were carefully weighed. The largest was 713 pounds. It seemed certain that this would win the prize. But just before the competition closed, a lorry arrived at the factory with a truly colossal biscuit which weighed 2,400 pounds. It had been baked by a college student who had used over 1,000 pounds of flour, 800 pounds of sugar, 200 pounds of fat, and 400 pounds of various other ingredients. It was so heavy that a crane had to be used to remove it from the lorry. The manufacturers had to pay more money than they had anticipated, for they bought the biscuit from the student for $24,000.

小题1:.

. Why have advertisers made a close study of human weakness?

A.They thought it was very interesting to do so.

B.They wanted to persuade the customers to buy their products.

C.They thought it was their duty.

D.They wanted to research how much people spend buying their products.小题2:.

. Why do advertisers offer free samples and other things to people?

A.They use them to attract people’s attention.

B.Their advertisements have little effect on customers.

C.Different means are being used to cheat people.

D.They produce too many products that can’t be sold out.小题3:.

From the last paragraph, we know that the factory failed to expect _______.

A.how many people would take an interest in the competition

B.how many ingredients are needed to bake a large biscuit

C.it was possible to bake a biscuit as large as the student’s

D.the payment wouldn’t be as high as $ 24,000