题目

化学反应N2＋3H22NH3的能量变化如下图所示，该反应的热化学方程式是( ) A．N2(g)＋3H2(g)2NH3(l)     ΔH＝2(a－b－c) kJ·mol－1 B．N2(g)＋3H2(g)2NH3(g)     ΔH＝2(b－a) kJ·mol－1 C.N2(g)＋H2(g)NH3(l)       ΔH＝(b＋c－a) kJ·mol－1 D.N2(g)＋H2(g)NH3(g)      ΔH＝(a＋b) kJ·mol－1 答案：答案 A 解析 通过图分析起点 mol N2(g)＋ mol H2(g)，变化三阶段为①吸收能量a kJ；②放出能量b kJ；③放出能量ckJ到mol NH3(l)。故可得热化学方程式：N2(g)＋H2(g)NH3(l) ΔH＝(a－b－c) kJ·mol－1，扩大计量数后得到A。 规律方法 解答与图象有关的简单计算题时，首先要弄清图象或图标的纵横轴表示的意义，由图象找About once a month I have to go to Bedford for my work. One day I went into a1there to have something to2. The waiter took my coat and put it in a small room. About an hour later I was3to go. The waiter4me my coat. Something fell out of the pocket onto the floor. It was a small white box. I took a5look at the6. “Oh, you’ve brought7coat,” I said to the waiter. “It looks very much like mine,8it is quite new, and this isn’t my box, either.” “Oh, then I9someone has taken your coat and left his,” said the waiter. “This kind of thing10sometimes.” I opened the box. There was a beautiful gold11in it. The waiter and I12to go to the police station. “Has anyone lost a ring?” I asked at the station. “Yes,” said a policeman. “A young man who came in this morning lost a ring, he lost it in London.” He13the young man. A few minutes later, the man arrived. “Yes, this is my ring,” he said. “How can I14you, sir? You see, I paid a lot of money for this ring and15I lost it on the train!” After I told him the16of the coat, he said, “You haven’t been on the train. I haven’t been in the hotel, so how did my ring17in the coat?” “Did anyone sit or stand next to you on the train?” asked the policeman. “Yes,” said the young man. “But I don’t remember his face.” “You may remember this18,” said the policeman. “Was it like this one?” “Yes, it was,” said the young man. “But my friend here isn’t the thief.” The policeman laughed. “No,” he said. “The thief on the train stole your ring, and19our friend here, he went into the hotel to get some food. Only he didn’t take the20coat away with him.”1.A.hotelB.restaurantC.companyD.shop2.A.doB.buyC.eatD.make3.A.askedB.gladC.invitedD.ready4.A.showedB.returnedC.broughtD.dressed5.A.specialB.closeC.usualD.near6.A.waiterB.boxC.coatD.pocket7.A.no one else’sB.another’sC.other’sD.someone else’s8.A.butB.andC.insteadD.for9.A.knowB.wonderC.supposeD.find10.A.appearsB.happensC.meetsD.changes11.A.ringB.coinC.penD.sign12.A.realizedB.thoughtC.wantedD.decided13.A.searchedB.rememberedC.telephonedD.asked14.A.returnB.thankC.payD.help15.A.thenB.soC.yetD.however16.A.thingB.priceC.storyD.problem17.A.comeB.putC.setD.get18.A.personB.ringC.boxD.coat19.A.afterB.beforeC.likeD.as20.A.rightB.goodC.sameD.other