题目

已知热化学方程式：C2H2(g)＋O2(g)＝2CO2(g)＋H2O(g) H＝－1256 kJ·mol－1。下列说法正确的是（ ） A．C2H2的燃烧热为1256kJ/mol B．若生成2mol液态水，则H＝－2512kJ/mol C．若转移10mol电子，则消耗2.5mol O2 D．若形成4mol碳氧共用电子对，则放出的热量为2512kJ 答案：【答案】C 【解析】燃烧热是指在一定条件下，1mol可燃物完全燃烧生成稳定的氧化物时所放出的热量，水的稳定状态是液态。A不正确。气态水生成液态是放出热量，B不正确。1mol氧气得到4mol电子，所以转移10mol电子，需要2.5mol氧气，C正确。形成4mol碳氧共用电子对，则生成2molCO2，放出的热量为1256kJ，所Once there lived an old man in a town. He always forgot a lot of things. So his wife always had to say to him，“Don't forget this.”     One day he went on a long way alone. Before he left home，his wife said，“Now you have all these things. You need them on your way. Take care of your things on the way.” He went to the station. He bought a ticket and got on the train with it.    About an hour later，the conductor began to see the tickets. He came to the old man and said，“Will you please show me your ticket?” The old man looked for his ticket in all his pockets but he could not find it. He was very worried.“I can't find my ticket. I really bought a ticket before I got on the train ” said the old man.    “I think you are right. I believe you bought a ticket. All right，you don't have to buy another ticket ” said the conductor kindly. But the old man still(仍然) looked worried and said sadly，“You don't know why I'm worried. If I don't find my ticket，I can't remember my station. Where am I going? ” 1.The old man bought a ticket _______. A. after he got on the train B. before he got on the train C. when the conductor told him to buy one D. when he found he had no ticket with him 2.About an hour later，the conductor began _______. A. to buy the tickets　　　 B. to look for the tickets C. to check(检查) the tickets　 D. to show the tickets 3. The conductor told the old man that he didn't need to buy another ticket because _________. A. the man was very old B. he thought the old man had no money with him C. the old man showed him the ticket D. he believed the old man 4.The old man still looked worried because _________. A. he couldn't get on the train. B. he lost his ticket and a lot of money C. he thought his wife would get angry with him D. he forgot where he was going 5.Which of the following(下列) is right? A. The old man went on the trip with his wife B. The old man didn't find his ticket C. The conductor was also an old man D. The old man had to buy another ticket