题目

．甲醇（俗名工业酒精）是一种“绿色能源”．甲醇完全燃烧的反应可表示为：2CH4O+xO22CO2+4H2O，其中x的数值和O2中氧元素的化合价分别是（ ） A．3，﹣2   B．3，0 C．6，﹣2   D．4，0 答案：【考点】有关元素化合价的计算；书写化学方程式． 【专题】化学用语和质量守恒定律． 【分析】根据由质量守恒定律：反应前后，原子种类、数目均不变，据此由反应的化学方程式推断x的数值即可；由单质中元素的化合价为0，计算O2中氧元素的化合价即可． 【解答】解：根据反应前后氧原子的数目单词拼写 (每题1分,共10题, 满分10分) 1.The change in climate may __________(影响) your health. 2.It is reported that only two people _______(幸存)the accident at last. 3.The ship _______(下沉)to the bottom of the sea after hitting an iceberg. 4.You've been working all morning---you __________(应得) a rest 5.He is good at ______(解决) this kind of problem. 6.The textbook c________ 10 units, including a mainly revision. 7.Our constitution (宪法)says that all men are e __________. 8.I would a________ it if you could help me with my English. 9.The teacher decided to d________ all his life to education. 10.In my o_________, I don’t agree with your plan.