问题 选择题

根据下表中几种固体物质在水中的溶解度,判断下列说法正确的是(  )

溶解度20℃80℃
NaCl3638.4
KNO331.6169

A.20℃时,在100g硝酸钾的饱和溶液中溶有31.6g硝酸钾

B.20℃时,在100g水中加入40g氯化钠,得到溶液的质量为140g

C.可以用冷却热饱和溶液的方法除去硝酸钾中混有的少量氯化钠

D.80℃的氯化钠的饱和溶液降温至20℃不会析出氯化钠晶体

答案

A、查阅20℃时硝酸钾的溶解度为31.6g,由溶解度的定义可以确定,100g水恰好可溶解31.6g硝酸钾达到饱和,所得饱和溶液为131.6g,而选项中溶液为100g,故A错;

B、由表格中的数据较易查到20℃时氯化钠的溶解度为36g,由溶解度的定义可以确定,100g水恰好可溶解36g氯化钠达到饱和,选项中所给溶质为40g,会剩余4g不能溶解,只能得到136g溶液,故B错;

C、冷却热饱和溶液提纯物质的适用范围是:两种固体可溶物,其一溶解度受温度变化影响较大,另一种物质溶解度受温度变化影响较小,对照两种物质的溶解度特点恰好符合,故C对;

D、氯化钠的溶解度变化特点为:溶解度随着温度的升高而增大,当由80℃降至20℃时,氯化钠的溶解度由38.4g降至36g,所以会析出晶体,故D错.

故选C.

阅读理解

阅读理解。

     Compared to people with bad attitudes , people who are cheerful and relaxed are less

likely to suffer from colds, according to a new study. " It'spossiblethatbeingupbeathelpsthe

bodyfight illnesses", says Sheldon Cohen, the study's lead researcher from Camegie Mellon

University( CMU) in Pittsburgh.

     In a previous study,Cohen and his colleagues put cold-causing viruses into the noses

of 334 healthy adults. People who tended to be cheerful and lively were least likely to

develop sniffles, coughs , and other cold symptoms. People who showed positive feelings

were also less likely to mention symptoms to their doctors , even whenmedical tests

detected those symptoms.

     Those findings were interesting, but they didn't prove that a person's attitude affects

whether he or she gets sick. Instead,it was still possible that a person's underlying

personality is what matters.Evidence suggests, for instance, that certain people are

naturally more likely to be outgoing and optimistic , with high self-esteem and a sense

of control over life. This would mean that who we are, not how we feel, ultimately

decides our chances of catching colds.

     To figure out which mattered more ( personality or emotions) , the CMU team

interviewed 193 healthy adults. The researchers talked to each person over the phone

every evening for 2 weeks. At the end of the interviewing period, people got nose drops

that contained either cold or flu viruses. Then, each person stayed in an isolated room

for 5 0r 6 days. The results showed that everyone in the study was equally likely to get

infected. Their symptoms, however, differed depending on the types of emotions that

they had reported over the previous 2 weeks. Among those who reported good moods

and had been infected with the flu virus, for example,28 percent developed coughs and

stuffy noses. On the other hand, those symptoms struck 41 percent of people who had

been less upbeat.

1. What would be the best title for the passage?_____

A. Smiles Turn Away Colds

B. An Interesting Way to Beat Colds

C. Be Outgoing and Optimistic to Fight Colds

D. What Matters More, Personality or Emotions?

2. In the previous study, people who showed positive feelings______

A. didn't catch colds as often

B. developed cold symptoms more slowly

C. were less likely to have cold symptoms detected

D. were less likely to feel cold symptoms

3. What mainly decides our chances of catching colds according to the new study?______

A. Personality. B. Self-esteem.

C. Emotions.D. Attitudes.

4. The underlined word " symptoms"probably means _________ .

A. something that causes cold

B. something that results in cold

C. signs that something exists , especially something bad

D. changes in your body or mind that show that you are not healthy

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