题干

下列各组溶液,不另加其他试剂就可以将它们分别开的是(  )

A:NaCl、HCl、NaAlO2、NaHCO3

B:NaSO4、KNO3、(NH42SO4、MgCl2

C:FeCl3、NaOH、AlCl3、HNO3

D:AgNO3、NaCl、NaSO4、NaI

上一题 下一题 0.0难度 选择题 更新时间:2016-01-25 11:36:19

答案(点此获取答案解析)

A,C

同类题1

阅读下面的文字,完成后面题。

高手

刘学林

    孔老四十岁当上处长,六十岁还是处长。自觉政绩不错。孔老不吸烟,不喝酒,不钓鱼,不养花,惟一的癖好是饭后茶余到街心花园观棋。观而不弈,无胜无败,无喜无怒,修养成鹤发童颜,仙风道骨。时间久了,棋盘上的各种高招绝技、阴谋杀机、圈套陷阱,尽皆谙熟。有时看双方棋艺悬殊,便给失利者指点几步,失利者无不茅塞顿开,反败为胜。于是聚在这里的棋迷们都尊他为高手。

    一天晚饭后,日光斜照,余热未散,晚霞未成。孔老摇一把雁翎扇,悠悠然来到街心花园。一群人重重叠叠围成浑厚的一圈,伸长脖子如长颈鹿一般。孔老凑上,目光如锥,可怎么也插不进人群去。他拍拍一小伙子肩膀,问:“谁和谁?”小伙子扭头一看,大喜,松出一口气,说:“这下好了,孔老来了。”众人一听,都如释重负一般,忙两边让开。孔老趋前,见是本土棋王老钟正和一面生的中年汉子对弈。老钟执红子,中年汉子执绿子。红帅已被兵困皇城,虽非一招即死,却也命在旦夕。故老钟眉头锁紧,目光凝结棋盘;中年汉子坦然自若,左手心玩健身球一样玩着两枚棋子,极熟练。孔老手摇羽扇,观透棋局,说:“舍炮杀士。”老钟看了一会儿,犹犹豫豫照办了。中年汉子落士杀炮干脆利索。孔老说:“进马。”老钟不再犹豫,因为他已看出对方如果不撤车逼马,就有一步高调马死棋。中年汉子果然撤车看马。红帅遂解围。之后过程中孔老又点拨两步,老钟竟然赢了中年汉子。

    中年汉子手中依然玩着两枚棋子,对孔老挑战地一笑,说:“我想向这位老同志请教一局。”“是我多嘴了。”孔老歉意一笑,又谦虚说,“对不起,我向来不下棋。”中年汉子说:“您刚才几步够绝的,怎么说向来不下棋呢?”孔老说:“我是向来不下棋。”中年汉子咄咄逼人:“那就请老同志破例赐教了。”孔老执意谦让,众人早已不平,纷纷怂恿:“孔老,你就和他下一局。”孔老说:“不下不下。”然而众人早已替他摆好棋子,不由分说簇拥他坐在中年汉子对面。“晚辈就先走了。”中年汉子说着已架起当头炮。孔老迫不得已,只好上马为应。才走几步,已觉局促如辕中驹,继之破绽屡出,先丢一炮,再折一车,不到十分钟,红帅已受靖康之辱。众人还以为孔老欲擒故纵,先礼后兵,就有人说:“好汉不赢前三局。”可是孔老此时却已面如死灰,汗进如豆,艰难一笑如哭,起身踉跄就走。

    回到家中,孔老很是沮丧。心想:我观那人棋艺并不算高明,我略加指点老钟,老钟便赢了他,可我亲自下场怎么会惨败如此呢?夜不成眠,静卧繁思,忽然大彻大悟,心明如镜。转天毅然写了退休报告。然后离开闹市,搬到市郊上街镇居住。

    依然爱观棋,不论在什么场合见到有人下棋必驻足观之。不觉十年。孔老越加出神入化,目光一扫便宏览全局,细察秋毫,棋观十步之外。偶尔给人点拨几步,对方不论是怎样高手,必败无疑。但绝不与人对弈。上街镇的象棋爱好者都把他奉为棋仙。这日,省青年象棋冠军到镇俱乐部辅导象棋,孔老自然前去观看。冠军名叫寇克,年轻有为又虚心好学。寇克和一青年表演赛时,孔老拈须站在青年身后。当青年处于困境时,孔老只说了一步棋就令寇克惊羡佩服之至,忙恭聆尊姓大名。孔老含笑不答,飘然而去。寇克问那青年,青年说大家都称老人棋仙,并不知老人名字。寇克怎肯放过这样好的机遇,打听到孔老住处,备下厚礼,登门请求赐教一局。孔老笑容可掬地一口回绝。寇克不肯罢休,学技心切,长跪不起。孔老无奈,叹一口气说:“你若心诚,三日后再来。”

    好不容易熬过三日,寇克急急登门。大门紧锁,久叩不开。问邻居,说孔老已经搬家。问搬到了何处,邻居摇头一笑,关上房门。寇克怅然痛惜,连说:“异人,异人!”孔老隔窗看寇克走远,拈须而笑。

同类题4

阅读理解

    Can you remember the first time you learned to ride a bike or drive a car? Learning theses kills changed your life forever and opened up new horizons (视野).Learning about computers can be like learning how to ride a bike or drive a car. Once you have employed the time to master the skills, you will never go back to the old days. The new technology is just too convenient and too powerful.

    Technological developments all through the years have enabled us to do more with less effort. We have continuously looked for better ways of doing things. Each invention and new development has allowed us to extend our capabilities. Today we see one of the most dramatic technologies ever developed—the computer. It extends the capabilities of our minds.

    Computers have saved organizations millions of dollars. Furthermore, these same computer systems have opened up new opportunities that would have gone undiscovered or ignored. There is no doubt that computers have a positive influence upon people's life, and the growth of computer usage is surprising. On the other hand, the computer can do serious damage. Invasion of privacy (侵犯隐私), fraud (欺诈),  and computer-related mistakes are just a few shocking examples. So the computer is like a double-edged sword. It has the ability to cut us free from some activities, but it can also cut deep into financial profits (利益), personal privacy and our society in general. The choice is yours, and only through a knowledge of computer systems will you be able to avoid the dangers while enjoying the many, many benefits of the computer age.