问题 问答题

如图中A、B、C分别表示三种物质的溶解度曲线.

(1)在t3℃时,三种物质的溶解度由大到小的顺序是______.

(2)在______℃时,B和C溶解度相同.

(3)t3℃时,A、B、C的饱和溶液各Wg,冷却至t1℃时,析出晶体最多的是______,没有晶体析出的是______.

(4)要在A、B、C混合物中分离C可用______的方法.

答案

(1)在t3℃时,三种物质的溶解度由大到小的顺序是C>B>A;

(2)在t1℃时,B和C溶解度曲线交于一点,二者的溶解度相等;

(3)由图可知:C的溶解度受温度影响最大,A的溶解度随温度的降低而增大,所以t3℃时,A、B、C的饱和溶液各Wg,冷却至t1℃时,析出晶体最多的是C,A无晶体析出;

(4)C的溶解度随温度升高而减小,与其他物质不同,所以可用升温、然后再过滤的方法将其分离出来;

故答案为:(1)C>B>A;(2)t1;(3)C;A;(4)升温.

单项选择题

Questions 53 to 57 are based on the following passage: ( 10 分 )  How did a peddler of cheap shirts and fishing rods become the mightiest corporation in America The short version of Wal-Mart’s rise to glory goes something like this:in 1979 it racked-up a billion dollars in sales; by 1993 it did that much business in a week; by 2001 it could do it in a day.  It’s a shocking tale--one that propelled Wal-Mart from rural Arkansas, where it was founded in 1962, to the top of the Fortune 500. Sam Walton, Wal-Mart’s founder, pushed sales growth continuously while squeezing costs with sophisticated information technology. He exhorted employees to sell better with the "ten-foot rule" ( greet customers if they are that close ). He was, in other words, an early evangelist for the first commandment of today’s economy: service rules. Wal-Mart, in fact, is the first service company to rise to the top of the Fortune 500. When Fortune first published its list of the largest companies in America in 1995, Wal-Mart didn’t even exist. That year General Motors was America’s biggest company, and in every year that followed,either GM or another mighty industrial, Exxon, was No.1.  Wal-Mart’s achievement caps a bigger economic shift I from producing goods to providing services. Manufacturing’s share ofU. S. employment peaked in 1953, at 35%. It has been declining steadily since. In the decade that will end in 2010, the Bureau of Labor Statistics figures that goods-producing industries will create 1.3 million new jobs, compared to 20 million for service industries. To look at it another way, today there are about four times as many people working in service jobs as in other kinds of jobs. And even within manufacturing, services are an increasingly large share of operations.  As America got richer, consumption got more complicated. With more income to throw around, people started spending more on services -- movies and travel, mortgages to buy houses, insurance to protect those houses, the occasional weekends at a luxury hotel. Fortune calls this a shift in the demand pattern. Over the next few years, only three of the ten fastest-growing occupations ( software engineers, nurses, and computer support ) pay middle-class salaries. The rest could be called Wal-Mart kinds of jobs -- cashiers, retail assistants, food service, and so on. In short, the service economy is delivering more good jobs than ever before.

In 1993, Wal-Mart could have a sales volume of two billion dollars in __

A.one week

B.two weeks

C.one day

D. two days

单项选择题