题干

某溶液中可能含有H+、Na+、NH4+、Mg2+、Fe3+、Al3+、SO42-、CO32-等离子。当向该溶液中加入一定物质的量浓度的NaOH溶液时,发现生成沉淀的物质的量随NaOH溶液的体积变化的图像如图所示。下列说法正确的是( )


A:原溶液中含有的阳离子是H+、NH4+、Mg2+、Al3+

B:原溶液中一定含有SO42-和Na+

C:原溶液中含有的Fe3+和Al3+的物质的量之比为1:1

D:反应最后形成的溶液中含有的溶质为Na2SO4

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答案(点此获取答案解析)

C

同类题1

阅读下面的文字,完成后面各题。

“微时代”,读什么?

    ①信息技术代有更替,近两年来,微信成为很多人的移动聊天室,用户已超过6 亿。君不见,候机室内,人人运指玩手机;地铁车厢,茫茫一片低头族。对许多人来说,“微信阅读”业已成为重要的阅读方式。

    ②订阅号渐渐增多,“选择”的问题也浮出水面。将各种内容推送给我的公共号,的确是我订阅的;而我订阅的,又是我感兴趣的。看不懂、不感兴趣、不认同其观点甚至仅仅是“讨厌这个帐号名”,都可以成为我不订阅、不看的理由,何况,订了我也可以不看,更不用说还随时能“取消关注”了。在这样的“自由选择”下,我的阅读趣味乃至知识水平,决定了我能看到什么。我读到的固然是我喜欢的,但我抛弃的却可能会更有价值。这就像是进入了一个认知的丛林,我无法走出“自我”这个陷阱。固化的欣赏口味与阅读取向,很可能让我无法去拥抱更为广阔的世界,寻求更为深刻的精神享受,甚至让我对世界的想象力开始萎缩。简单点说,太舒服的阅读。让我无法“突破”,甚至原地踏步。

    ③虽然没有大数据支撑,但微信的普遍状况,却也证明着这样的观点。朋友圈中分享的公共帐号页面,很多都有“揭秘”“爆料”“有染”等种种令人惊悚词汇,更不乏“不得不看的人生格言”“30 岁之前要明白的50个道理”等或浓或淡的心灵鸡汤。多有无法深究的八卦,多有似是而非的劝诫,多有浅尝辄止的思考,多有不知所云的感悟……有人调侃说,这样的分享,说者未必懂,而听者也未必信,不过是在寻求饭局上的谈资。这样的阅读状况,难免会让人担心背后日渐失血的心灵图景。

    ④更重要的是,每天更新的订阅人数、页面访问量,让公共帐号的提供者们,精准地掌握着读者的口味,从而不断满足甚至迎合着读者的阅读偏好。这样的“正反馈效应”,将使这个新的阅读市场越来越像一个提供廉价用品的超市。你的选择,也决定了你可能有的选择。人人爱八卦,则高谈阔论种种内幕、秘闻的内容就增多;个个爱鸡汤,则励志类、成功学、创业经难免泛滥。

    ⑤有人说,世界上种种变动中的关系,只有两种状态,要么是良性循环,要么是恶性循环。而让人欣慰的是。这两种循环是可以转化的。在微信阅读可能出现的循环状态中,只要有一方愿意迈出一步,就会改变其发展的走向。对于读者来说,走出心灵之宅,克服懒惰或是畏难心理,努力寻找“高一层次”的阅读,去理解那些你或许不同意的观点,去欣赏那些你或许不喜欢的表达,在这个过程中肯定能发现那一片“林中空地”。而对于微信公共帐号——这些文化产品的提供者们来说,则需要保持恒定的审美价值观,在分析与把握受众需求的同时,以更高远的眼界开拓更丰富的资源,不被枯燥的数字牵着鼻子走。

    ⑥希望那些微信阅读时代的公共帐号,以及那些不远的未来将会发生的更多阅读变革,在改变我们阅读的同时,也能给予我们以真正的幸福。

(选自《人民日报》,有删改)

同类题5

七选五

    Fun doesn't have to be expensive

    Everyone likes to have fun, but not everyone has much money to spend. Here are some free or cheap ways to enjoy yourself.

    Go outside

    Going outside in good weather can be a lot of fun if you don't want to stay at home. ____ If you live in a city, you can go window-shopping. Or you can explore an old part of town and admire the buildings.

    Try a hobby

    While you're out, take pictures of things you find. Planning and taking pictures can make you aware of the beauty all around you. Photographic equipment can be expensive, but it doesn't have to be. You probably already own a camera or a cell phone that can take pictures. Other creative hobbies can also be done with basic materials. ____

    Find an event

    Libraries often hold free public events. ____And while you're there, borrow a book or movie for free. Museums and universities also hold free events.

    If you can't find a free event, you can volunteer at an event that requires tickets. People who organize concerts and plays need help.____ Sometimes they reward volunteers with free tickets.

    Meet a friend

    Relationships are often the best things in life. ____ For example, invite a friend for a walk, an event or a time working on your hobby. Hosting doesn't have to be difficult. If your friend comes in the afternoon, you don't have to serve a meal. You can sit and talk, play board games or card games or watch a movie together.

A. A friend in need is a friend indeed.

B. Stop by one to find out what's going on.

C. Hike or bicycle with a friend on a nearby path or in a park.

D. Whatever you do, find a friend to share it with.

E. It's a good idea to stay at home to watch a movie.

F. You can set up or take down chairs or greet visitors.

G. Drawing and writing require nothing more than a pencil and paper.