二甲醚（C2H6O）是一种重要的化工原料，下列关于二甲醚的说法错误的是
A．每个分子中含有9个原子
B．属于氧化物
C．碳、氢、氧元素质量比为12：3：8
D．碳元素的质量分数约为52.2%
答案：B
题目分析：根据二甲醚的化学式为C2H6O分析。
A、—个二甲醚分子是由2个碳原子、6个氢原子和1个氧原子构成的，则—个二甲醚分子中含有9个原子，正确；
B、氧化物是由两种元素组成，其中一种是氧元素的化合物，而C2H6O是由碳、氢、氧三种元素组成的，错误；
C、二甲醚中C、H、O三种元素的质量比=（12×2）：（1×6）：（16×1）=12︰3︰8，正确；
D、根据元素的质量分数=
×100%可知，C2H6O中碳元素的质量分数=
×100%=52.2%，正确。故选B
点评：本题难度不大，熟练掌握化学式的宏观与微观意义，以及有关化学式的计算，并能灵活运用是正确解答本题的关键。
In the past，people usually believed what newlyborn babies wanted was food and to be kept warm and dry.They thought babies were not able to ____ things until they were five or six months old.____ the researchers in the United States now believe babies begin learning on their first ____ of life.They say babies are strongly ____ by their environment and one baby will ____ if his or her mother does something that the baby likes. A baby learns to get the best care possible by smiling to ____ her mother.This is how babies start to learn to ___ and communicate with other people.The researchers say this ability to learn ___ in a baby even before birth.They also ____ the idea that newlyborn babies can ____ and understand sounds they heard while they were still ____ inside their mothers. Recently，an American study ____ 112 babies found babies learned better when they were ____.The babies appeared to learn well whether they were sitting up on their own，sitting in seats or __ to sit up.The researchers say keeping that kind ____ had what they called a ____ effect on the babies' ability to learn about objects.They say the body position may be linked to development in the ____．One ____ says babies can pay more attention to ___ an object if they do not have to be worried about their balance.
|