问题 填空题

将蔗糖与稀硫酸的混合液煮沸后,分成两份:向一份溶液中加入银氨溶液,加热,产生白色沉淀,无银镜生成;向另一份溶液中加入新制的氢氧化铜悬浊液,无砖红色沉淀产生。试写出有关反应方程式,并解释实验现象。

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答案

 C12H22O11(蔗糖)+H2OC6H12O6(葡萄糖)+ C6H12O6(果糖),2Ag(NH3)2OH+ 

3H2SO4=Ag2SO4↓+ 2(NH4)2SO4+2H2O,Cu(OH)2+H2SO4=CuSO4+2H2O,由于未加NaOH溶液中和起催化剂作用的稀硫酸,Ag(NH3)2OH与H2SO4反应生成Ag2SO4沉淀,故没有银镜生成;Cu(OH)2溶于H2SO4生成CuSO4,故没有Cu2O沉淀生成。

多项选择题
阅读理解

阅读理解。

     No one else knew about the extra club in Zach Nash's golf bag. It belonged to a friend, and Zach forgot

it was there as he played his way to victory in a junior tournament (锦标赛) last summer in Wisconsin, US.

     The 14-year-old accepted his medal, celebrated with his grandparents who had come from a long way

to watch. But when he stopped by his country club to share the news, a professional player noticed something

wrong. "Count your clubs," he told the teenager.

     Fifteen-one more than allowed. Zach's eyes filled with tears.

     If Zach had just won a basketball championship or a soccer game and someone had discovered a violation

after the win, it would not have mattered. It is nothing unusual for a soccer player to dive to the turf to draw

fouls (假摔以使对方犯规).

     Golf is different. In a win-at-all-costs world, the game holds itself to a higher standard. Golf isn't a game

where referees watch closely. In golf tournaments, dozens of competitors are spread across acres of land, so

officials cannot hope to see each shot. Competitors call penalties (处罚) on themselves.

     "It was a sport for gentlemen, and gentlemen did not care about winning. They care about doing the right

thing," said Robert Simon, a golf coach at Hamilton College in New York.

     Honesty became a medal of honor. When one of the game's early stars, Bobby Jones, was praised for

calling a penalty on himself at the 1925 US Open, he replied:"You might as well praise a man for not robbing

a bank."

     So even the error had no effect on Zach's final score-he has never used the extra club, the teenager packed

up his medal and dropped it in the mail. "But this is golf, and rules are rules. I just knew what I had to do," he

said.

     Then came another tournament. Before teeing off (开球), Zach counted his clubs-four times.

1. What can we infer from the text?

A. A friend put an extra club in Zach's bag.

B. Zach returned the medal that he had won.

C. Zach's grandparents encouraged him to play fair.

D. Zach regretted meeting with the professional player.

2. According to Robert, golf is different from other sports in that _____.

A. honor comes before victory

B. players are superior to coaches

C. referees have to watch each shot

D. players needn't care about medals

3. What can be learned from the underlined sentence?

A. One should be praised-for not robbing a bank.

B. Bobby looked down upon bank robbers.

C. Little did Bobby care about the penalty.

D. Observing rules demands no praise.

4. Why did Zach count his clubs four times before the following tournament?

A. He remembered the lesson.

B. He lacked self-confidence.

C. He felt a little too nervous.

D. He was no good with numbers.