题目

乙酸乙酯(C4H8O2)是一种有浓郁香味、难溶于水的油状液体，常用作食品或饮料的调香剂。下列有关乙酸乙酷的叙述正确的是A. 乙酸乙酯属于氧化物B. 乙酸乙酯中碳、氢、氧元素的质量比为4:8:2C. 乙酸乙酯是由4个碳原子、8个氢原子、2个氧原子构成的D. 乙酸乙酯中碳元素的质量分数大于氧元素的质量分数 答案：【答案】D【解析】A. 由化学式可知，乙酸乙酯由碳、氢、氧三种元素组成，不属于氧化物，选项错误；B. 乙酸乙酯中碳、氢、氧元素的质量比为（12×4）:（1×8）:（16×2）=6:1:4，选项错误；C. 一个乙酸乙酯分子是由4个碳原子、8个氢原子、2个氧原子构成的，选项错误；D. 乙酸乙酯中碳、氢、氧元素的质阅读填空（共2小题）阅读下列短文，根据短文中的信息完成文后表格。在答题卡标有题号的横线上，写出空缺处所填单词的正确形式（每空一词）Any time of the day you can devote to exercising is a good time for getting active, but if you want to make a healthy fitness plan, it may be helpful to keep several points in mind and find out the best time to exercise．First, try to know what kind of person you are．Especially, are you an early bird who always wakes up early in the morning, or a night owl(猫头鹰)who almost never goes to bed before midnight? Once you are generally aware of what your sleep characteristics are, you will have a better understanding of when your body needs exercise, either early in the morning, sometime during the day, or later on in the evening．Second, consider your daily plan．When do you seem to be most busy, and when do you plan your most important tasks? Try to fit in your exercise before or at least around these events if possible, so that you can keep exercising and your life won't be influenced as well．Third, think about when you feel you have the most energy．For most people, that time is usually in the morning after a good night's rest, or after a long day of work．After a busy or much stressful day, exercising can reduce your working stress from hard work．Lastly, find out the place you plan to do exercise．Your house provides exercise at any time if you own fitness equipment(设备)，but if there is a gym(健身房)down the street or along the way home from work, it will make it more suitable for you to exercise．More importantly, you need to make a plan and try sticking to it for one week．If you do so and can get through the exercise without being pulled in another direction, make it a habit．And once you have set up your fitness plan, don't make any great changes to it unless your doctor allows you to．