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问题 问答题

如图是常见固体物质的溶解度曲线．

（1）M点的意义是______

（2）在t2℃将20gA物质放入50g水中，所得溶液为______（填“饱和”或“不饱和”）溶液，再升温至t3℃，所得溶液的质量为______；

（3）t3℃时A、B、C三种物质饱和溶液的质量分数由大到小的顺序是______，若将t3℃时A、B、C三种物质的饱和溶液降温至t1℃，溶液中溶质质量分数最大的是______物质．

答案

（1）M点是AB在t2℃时溶解度曲线的交点，表示t2℃时AB的溶解度相等；

（2）t2℃时A的溶解度是30g，所以将20gA物质放入50g水中，最多溶解15g，所得溶液为饱和溶液，t3℃时A物质的溶解度是50g，50g水最多可溶解30g的A，所以得到的溶液的质量是70g；

（3）t3℃时A、B、C三种物质的溶解度大小关系是A＞B＞C，由饱和时质量分数的计算式

溶解度
溶解度+100g
×100%可知，溶解度越大质量分数也就越大，所以此时饱和溶液的质量分数由大到小的顺序是A＞B＞C；AB的溶解度随温度的降低而减小，C的溶解度随温度的降低而增大，所以若将t3℃时A、B、C三种物质的饱和溶液降温至t1℃，AB析出晶体为饱和溶液，t1℃时B的溶解度大于A，C变为不饱和溶液，其溶质的质量分数与t3℃时相同，观察图示可知t1℃时B的溶解度大于t3℃时C的溶解度，所以溶液中溶质质量分数最大的是B；

故答案为：（1）t2℃时AB的溶解度相等；

（2）饱和；70g；

（3）A＞B＞C；B．

单项选择题

People are indulging in an illusion whenever they find themselves explaining at a cocktail (鸡尾酒) party, say, that they are "in computers," or "in telecommunications," or "in electronic funds transfer". The implication is that they are part of the high-tech world. Just between US, they usually aren’t. The researchers who made fundamental breakthroughs in those areas are in a high-tech business. The rest of us are (71) of their work. We use computers and other new technology components to develop our products or to organize our affairs. Because we go about this work in teams and projects and other tightly knit working groups(紧密联系在一起的工作小组), we are mostly in the human communication business. Our successes stem from good human interactions by all participants in the effort, and our failures stem from poor human interactions.

The main reason we tend to focus on the (72) rather than the human side of the work is not because it’s more (73) , but because it’s easier to do. Getting the new disk drive installed is positively trivial compared to figuring out why Horace is in a blue funk (恐惧) or why Susan is dissatisfied with the company after only a few months. Human interactions are complicated and never very crisp (干脆的, 干净利落的) and clean in their effects, but they matter more than any other aspect of the work.

If you find yourself concentrating on the (74) rather than the (75) , you’re like the vaudeville character (杂耍人物) who loses his keys on a dark street and looks for them on the adjacent street because, as he explains, "The light is better there!".

 

71（）

A．creators

B．innovators

C．appliers

D．inventors
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判断题

羊奶在国际营养学界被称为是“奶中之王”，其维生素和微量元素的含量都明显高于牛奶。（）
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