问题 选择题

蔗糖是生活中常用的调味品,其溶解度曲线如图.下列说法正确的是(  )

A.蔗糖在热水中的溶解度比在冷水中的小

B.将蔗糖饱和溶液蒸发溶剂后恢复至原温度,有结晶现象

C.温度升高,溶液中蔗糖的质量分数一定增大

D.t1℃和t2℃时的两份蔗糖溶液,所含溶质的质量不可能相等

答案

A、由于蔗糖的溶解度随温度的升高而增大,故A错误;

B、给蔗糖的饱和溶液蒸发溶剂再恢复到原来的温度,则原来溶解在这部分溶剂中的溶质就会结晶析出,故B正确;

C、如果只是单纯的温度升高,在不考虑溶剂蒸发的情况下,溶液中若没有未溶解的溶质存在,则溶液中溶质的质量分数则不发生变化,故C错误;

D、由于温度高的溶解度就大,只能说这两个温度下的饱和溶液中溶质的质量分数不可能相等,但溶液所含溶质的质量可能相等,故D错误;

故选B.

单项选择题
阅读理解

     One stormy night many years ago, an elderly man and his wife entered the hall of a small hotel in

Philadelphia. Trying to get out of the rain, they came the front desk hoping to get some shelter for the

night.

     "Could you possibly give us a room here?" the husband asked.

     The clerk, a friendly man with a winning smile, looked at the couple and explained that there were

three conventions in town. "All of our rooms are taken," the clerk said. "But I can't send a nice couple

like you out into the rain at one o'clock in the morning. Would you perhaps be willing to sleep in my

room? It's not exactly a suite, but it will be good enough to make you folks comfortable for the night."

     When the couple declined, the young man pressed on. "Don't worry about me; I'll make out just fine."

the clerk told them.So the couple agreed.

     As he paid his bill the next morning, the elderly man said to the clerk, "You are the kind of manager

who should be the boss of the best hotel in the United States. Maybe someday I'll build one for you."

The clerk looked at them and smiled. The three of them had a good laugh. As they drove away, the

elderly couple agreed that the helpful clerk was indeed exceptional, as finding people who are both

friendly and helpful isn't easy.

     Two years passed. The clerk had almost forgotten the incident when he received a letter from the old

man. It recalled that stormy night and enclosed a roundtrip ticket to New York, asking the young man to

pay them a visit.

     The old man met him in New York, and led him to the corner of Fifth Avenue and 34th street. He

then pointed to a great new building there, a pale reddish stone, with turrets and watchtowers thrusting

up to the sky. "That," said the older man, "is the hotel I have just built for you to manage." "You must be

joking, " the young man said. "I can assure you I am not," said the older man, a sly smile playing around

his mouth.

     The older man's name was William Waldorf Astor, and that magnificent structure was the original

WaldorfAstoria Hotel. The young clerk who became its first manager was George C. Boldt. This young

clerk never foresaw the turn of events that would lead him to become the manager of one of the world's

most glamorous hotels.

1. The purpose of the following author writing this story is to________.

A. give people a good laugh

B. cover some facts

C. promote the business of WaldorfAstoria Hotel

D. deliver a lesson

2. Which of the following statements about the story is NOT true ?

A. The story took place at about one a. m..

B. The old couple was too poor to afford a luxurious room.

C. The clerk was willing to help those in need.

D. The clerk received an unexpected invitation from the old man.

3. The underlined word "conventions" in Para 3.can be replaced by________.

A. rooms    

B. suites

C. meetings    

D. hotels

4. Which of the following proverbs suits the story the best?

A. Every little thing helps.

B. Make hay while the sun shines.

C. Man proposes; God disposes (处理, 决定).

D. One good turn deserves another.