题干

粗盐水过滤后仍含有可溶性的CaCl2、MgCl2、Na2SO4等杂质,通过如下几个实验步骤可以除去这些杂质. ①加入稍过量的Na2CO3溶液;②加入稍过量的NaOH溶液;③加入稍过量的BaCl2溶液;④滴入稀盐酸至无气泡产生;⑤过滤.正确的操作顺序是(   )

A:③②①⑤④

B:②③①④⑤

C:①③②⑤④

D:③⑤②①④

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答案(点此获取答案解析)

A

同类题1

阅读下面的短文,根据短文内容及首字母提示,在短文空白处填入一个恰当的词,使短文内容完整、通顺,并将所填单词填写在答题卡上相应的题号后。

    I packed, and was ready to leave for my two-day trip. I had been busy with my work. I had made p____ for the trip for the last few days, and I expected to get r____ for several days. As I got into the car to leave, my mind flew to my kids.

    How to keep in touch with your kids when you're busy or far away is a dilemma(两难的问题) many fathers have. Men like to focus special attention on one thing for a long p____, but this can lead to trouble. Moving from work to family isn't always an easy thing. And if you don't s____ your kids that you're thinking about them, they may think that you don't care.

    As I started down the road, I suddenly stopped to t____ back to my house and wrote a short message on a c____ of cards to each of my children. I put each in a “secret” place where I knew they'd find it. When I called the next night, they both said e____, “Daddy, I got your card. When did you do that?”

    I was moved when I heard these words. What I had never thought was that a small thing had a big influence on my kids. It proved(证明) that they were in my heart. And distance (距离) couldn't s____ them from their father. To my satisfaction, they feel “love” of their father. This v____ experience encouraged me to continue to do the small things to be a responsible father.

    As fathers get much busier and have to work longer hours, they usually pay l____ attention to the small things. Don't miss the good chances to let your kids see how important they are.

    Take a moment to do a small thing for your kids. It won't s____ small to them.

同类题4

阅读下面的文字,完成下列各题。

    我相信熟练的读者大概都有这样一种能力,去书店买书或是到图书馆找书,拿起一本书很迅速地翻一翻,一两分钟之内,就能大概知道这是一本什么样的书。这个印象也许并不准确,但是它能够起到一个初步的导航作用。然而电子书却做不到这一点,因为电子书是不能“翻”的,即使可以跳页浏览,你还是会觉得它慢。

    意大利著名学者安伯托•艾可认为,即使我们会有越来越多的电子阅读器,但书这个东西是一个非常好的发明,是不能被改进、不会被替代的发明。就像剪刀、车轮或者勺子一样,这些东西自从问世之后,就几乎没怎么变过,我们一直在使用,也不嫌它们落伍,也许需要小修小补,但整个形态上的大规模的变化是不必要的。

    法国知名电影学者尚•克洛德•卡里耶尔说,25年前,他在巴黎坐地铁的时候,总是会遇见一个坐在地铁站的长椅上好像在等车的人,这个人身边总有四五本书,天天坐在那里看书。有一天他终于忍不住好奇,过去问这个人到底在干吗,这个人说了让卡里耶尔难忘的一句话:我就是在读书。至于为什么选择在地铁站里读书,是因为那里是唯一一个不用消费就可以一直坐着的地方,而且冬暖夏凉。“我很快走开了,因为我意识到自己在浪费他的时间。”卡里耶尔说。

    正是因为如此,所以,永远别想摆脱书。

(《别想摆脱书》梁文道)