题干

下列除去杂质的方法正确的是(   )

①除去乙烷中少量的乙烯:光照条件下通入Cl2,气液分离

②除去乙酸乙酯中少量的乙酸:用饱和碳酸钠溶液洗涤,分液、蒸馏

③除去C2H6中少量的C2H4:气体通过盛有酸性高锰酸钾溶液的洗气瓶

④除去乙醇中少量的乙酸:加足量生石灰,蒸馏.

A:①②

B:②④

C:③④

D:②③

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答案(点此获取答案解析)

B

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    “Mum, what does it mean when someone tells you that they have a skeleton(骨骼) in the closet?” Jessica asked. “A skeleton in the closet?” her mother paused thoughtfully. “Well, it's something that you would rather not have anyone else know about. For example, if in the past, someone in Dad's family had been arrested for stealing a horse, it would be ‘a skeleton in his family's closet'. He really wouldn't want any neighbor to know about it.”

    “Why pick on my family?” Jessica's father said with anger. “Your family history isn't so good. You know. Wasn't your great-great-grandfather a prisoner who was sent to Australia for his crimes?” “Yes, but people these days say that you are not a real Australian unless your ancestors arrived as prisoners.” “Gosh, sorry I asked, I think I understand now,” Jessica cut in before things grew worse.

    After dinner, the house was very quiet. Jessica's parents were still quite angry with each other. Her mother was ironing clothes and every now and then she glared at her husband, who hid behind his newspaper pretending to read. When she finished, she gathered the freshly pressed clothes in her arms and walked to Jessica's closet. Just as she opened the door and reached in to hang a skirt, a bony arm stuck out from the dark depths and a bundle of white bones fell to the floor. Jessica's mother sank into a faint(晕倒), waking only when Jessica put a cold, wet cloth on her forehead. She looked up to see the worried faces of her husband and daughter.

    “What happened?Where am I?” she asked. “You just destroyed the school's skeleton, Mum,” explained Jessica. “I brought it home to help me with my health project, I meant to tell you, but it seemed that as soon as I mentioned skeletons and closets, it caused a problem between you and Dad.” Jessica looked in amazement as her parents began to laugh madly. “They're both crazy,” she thought.