题目

在化学反应2A+B2=2C中，已知20gA和足量B2充分反应后，生成30g C．已知B2的相对分子质量为32，则C的相对分子质量是 （ ） A．20B．32C．48D．96 答案：分析：依据质量守恒定律可知反应物B2的质量，进而确定了B2和C的质量关系，然后依据化学反应中物质之间的质量比等于其相对分子质量和的比求解即可． 解答：解：根据质量守恒定律可知20gA和B2充分反应生成30gC时参加反应的B2质量应为30g﹣20g=10g； 设C的相对分子质量是x，则 2A+B2=2C    32 2x   10g 30g = A thief who dropped a winning lottery ticket(彩票)at the scene of his crime has been given a lesson in honesty. His victim, who picked up the ticket, then claimed the ￡25000 prize, managed to trace him, and handed over the cash. The robbery happened when maths professor Vinicio Sabbatucci,58, was changing a tyre on an Italian motorway. Another motorist, who stopped  "to help", stole a suitcase from his car and drove off. The professor found the dropped ticket and put it in his pocket before driving home to Ascoli in eastern Italy.     Next day, he saw the lottery results on TV and, taking out the ticket, realized it was a winner. He claimed the 60 million lire(里拉) prize. Then he began a battle with his conscience. Finally, he decided he could not keep the money despite having been robbed. He advertised in newspapers and on radio, saying: "I'm trying to find the man who robbed me. I have 60 million for him--- a lottery win. Please meet me. Anonymity(匿名) guaranteed."     Professor Sabbatucci received hundreds of calls from people hoping to trick him into handing them the cash. But there was one voice he recognized--- and he arranged to meet the man in a park. The robber, a 35-year-old unemployed father of two, gave back the suitcase and burst into tears. He could not believe what was happening. "Why didn't you keep the money?" he asked. The professor replied:" I couldn't because it's not mine." Then he walked off, spurning the thief's offer of a reward.     60 .The sentence " Then he began a battle with his conscience." In paragraph 2 implies all of the following EXCEPT that_______.     A. he came to realize that honesty is more important than money       B. he hesitated about keeping the money for some time     C. he knew what he should do as soon as he saw the lottery results     D. he thought for a moment of avenging（为...报仇）himself on the robber    61 . Hundreds of people phoned professor Sabbatucci because they ______.     A. wanted to make fun of him        B. knew who the robber was   C. hoped to get the money           D. lost the lottery ticket       62.The underlind word "spurning" in the last sentence can be replaced by ______.     A. accepting      B. rejecting       C. claiming      D. canceling     63. If the story appears in a newspaper, the best title might be_____.     A. A Reward of Honesty        B. A Popular Maths Professor       C. A Magic Lottery              D. A Thief's Lucky Day