题干

以硫酸铜溶液作电解液,对含有杂质Fe、Zn、Ag的粗铜进行电解精炼.下列叙述正确的是(  )

①粗铜与直流电源负极相连   

②阴极发生的反应为Cu2++2e=Cu

③电路中每通过3.01×1023个电子,得到的精铜质量为16g

④杂质Ag以Ag2SO4的形式沉入电解槽形成“阳极泥”


A:②③    

B:②④ 

C:③④   

D:①③

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答案(点此获取答案解析)

A

同类题2

阅读下文,完成后面1—5题。

唱歌的人

沈家禄

在报社旁边的小店吃面,门外的风吹得紧,街上几乎是漆黑一片,我要了一碗辣酱面。吃到一半,门被大大地推开了,西北风乘机往我衣领里钻。三个小伙子,一个背着吉他,一个拿着萨克斯,一个双手甩着沙球就唱起了歌。他们是对着一张坐满了客人的桌子唱的,那桌子人在吆五喝六地喝着酒,菜盘子一个叠一个,一个火锅冒着热气。但是这拨客人挥挥手,像赶苍蝇似的叫他们走。他们又来到一张小方桌前,四个小青年在喝酒,喝啤酒。“快走吧。”他们的声音显出更加不耐烦。唱歌的三个人来到角落里,两个中年客人在吃馄饨,他们说:“你们唱也是白唱,我们没有钱给你们。”这三个小伙子只得怏怏地走了。

我叫住了他们。“你们吃晚饭了没有?”他们愣了一下,就来到我面前准备开口。我没让他们唱,而是给他们每人要了一碗排骨面。店主有点纳闷,但还是吩咐手下人去做了。他们三个穿着相似的衣服,浅米色的粗呢西装,起皱的地方看样子是熨不平了,外套里面穿得不多,但他们情绪还不错,说话干脆利索,时不时地看看同伴,笑一下。他们皮肤黝黑,很瘦,从辽宁来到上海,看看,顺便赚点钱。我问他们会唱什么歌,他们说老歌新歌都会,太多了。

面上来了,但他们不动筷。说:“还是你吃吧,叫我们怎么咽得下。”我说我有胆囊炎,不能吃大肉。于是他们说了声“不客气了”就吃起来了。我不再问他们更多的问题,怕产生误会,好像我请他们吃面就有了询问他们的权利。他们好像没怎么嚼就吃完了,犹豫了一下把汤也喝下去了,站起来问我想听哪支歌。我一手按住吉他的弦,说我还要上班。

结了账,店主嘀咕一声:“你做了好人,他们明天就还会再来。”我说让他们来吧,给他们吃面,账算在我头上。旁桌客人中传来笑声:“天下饿肚子的人多了,给一碗排骨面就能做慈善家了?”我没理他们。三个辽宁小伙子听不懂上海话,但觉出味道不对,就问我要不要揍那些人一顿。我把他们推出门外。

没想到我走在前面,他们就紧跟着我唱起来。我挥手阻止他们,吉他手说:“我们喜欢唱,有时候憋在心里发堵,还是唱出来痛快。”他们一个弹吉他,一个吹萨克斯,一个手甩沙球,就在夜色沉沉的街上边走边唱起来。我在脚下加了点力,一转身进了报社大门。回身一看,三个小伙子就站在不远的路灯下,声音更加响亮,很高兴的样子,风吹起了他们的衣角。我心里感激着他们,后来这种情绪慢慢地变成了羞愧。我真是羞愧极了。


同类题3

阅读下面四篇短文,从每题所给的A、B、C、D四个选项中选出最佳选项。

B

 

    Think of life as a game in which you are playing with five balls in the air. You name them work, family, health, friends and spirit and you keep all of them in the air. You will soon understand that work is a rubber ball. If you drop it, it will bounce back.  

    But the other four balls, family, health, friends and spirit, are made of glass. If you drop one of these, it will be broken and never be the same. You must understand that and try to have balance in your life. How ?  

    Don't look down on your worth by comparing yourself with others. It is because we are different and each of us is special.  

    Don't let other people set goals for you. Only you know what is best for yourself.  

    Don't give up when you still have something to give. Nothing is really over until the moment you stop trying.

    Don't be afraid of difficulties. It is by taking chances that we learn how to be brave.

    Don't shut love out of your life by saying it's impossible. The quickest way to receive love is to give it; the fastest way to lose love is to hold it too tightly; the best way to keep love is to give it wings.  

    Don't run through life so fast that you forget not only where you've been, but also where you are going.  

    Don't be afraid to learn. Knowledge is weightless. It's a treasure you can always carry easily.  

    Don't use time or words carelessly. You can't get them back. Yesterday is history, tomorrow is a mystery*, and today is a gift; that's why we call it “the present”. Life is not a competition, but a trip, step by step.