问题 选择题

下列实验方案设计中,不可行的是

A.加足量稀盐酸后过滤,除去混在铜粉中的少量铁粉

B.在一定条件下利用氯气与铁反应生成FeCl3

C.用稀盐酸和硝酸银溶液检验溶液中Cl

D.用氢氧化钠溶液和湿润红色石蕊试纸检验溶液中的NH4+

答案

答案:C

题目分析:A中加入稀盐酸后铁粉被反应掉,铜粉不反应,所以能够达到实验目的。B中铁和氯气直接反应生成FeCl3,所以能够达到实验目的。C中稀盐酸本身还有Cl-,所以不能达到实验目的。D中NH3能使湿润的红色石蕊试纸变蓝,所以能够达到实验目的。

点评:1.常见阳离子的检验

离子检验方法现象
K+用铂丝蘸取待测液放在火上烧,透过蓝色钴玻璃(过滤黄色的光)火焰呈紫色
Na+用铂丝蘸取待测液放在火上烧火焰呈黄色
Mg2+加入OH-(NaOH)溶液生成白色沉淀[Mg(OH)2],沉淀不溶于过量的NaOH溶液
Al3+加入NaOH溶液生成白色絮状沉淀[Al(OH)3],沉淀能溶于盐酸或过量的NaOH溶液,但不能溶于氨水(Al(OH)3+OH-→AlO2-+2H2O)
Ba2+加入稀硫酸或可溶性硫酸盐溶液生成白色沉淀(BaSO4),沉淀不溶于稀硝酸
Ag+①加入稀盐酸或可溶性盐酸盐生成白色沉淀(AgCl),沉淀不溶于稀硝酸
②加入氨水生成白色沉淀,继续滴加氨水,沉淀溶解
Fe2+①加入少量NaOH溶液生成白色沉淀[Fe(OH)2],迅速变成灰绿色,最终变成红褐色[Fe(OH)3](4Fe(OH)2+O2+2H2O→4Fe(OH)3
②加入KSCN溶液无现象,再加入适量新制的氯水,溶液变红
 Fe3+①加入KSCN溶液溶液变为血红色
②加入NaOH溶液生成红褐色沉淀
NH4+加入强碱(浓NaOH溶液),加热产生刺激性气味气体(NH3),该气体能使湿润的红色石蕊试纸变蓝。
2.常见阴离子的检验

离子检验方法现象
Cl-加入AgNO3溶液生成白色沉淀(AgCl)。该沉淀不溶于稀硝酸,能溶于氨水
SO42-先加入HCl再加入BaCl2溶液(加H+防CO32-干扰;加HCl防Ag+干扰;不用HNO3防 SO32-干扰)生成白色沉淀(BaSO4),该沉淀不溶于稀硝酸
 SO32-①加入盐酸或硫酸产生无色、有刺激性气味的气体(SO2),该气体可使品红溶液褪色
②加BaCl2,生成白色沉淀(BaSO3该沉淀可溶于盐酸,产生无色、有刺激性气味的气体(SO2
CO32-①加入CaCl2或BaCl2溶液生成白色沉淀(CaCO3或BaCO3),将沉淀溶于强酸,产生无色、无味的气体(CO2),该气体能使澄清的石灰水变混浊
②加入盐酸产生无色、无味的气体,该气体能使澄清的石灰水变浑浊;向原溶液中加入CaCl2溶液,产生白色沉淀
HCO3-加入盐酸产生无色、无味的气体,该气体能使澄清的石灰水变浑浊;向原溶液中加入CaCl2溶液,无明显现象

问答题

Vilhelm Hammershoi has been a well-kept secret since his death in 1916. All his best- known paintings are of household interiors that are drained of color and tell no stories. 46. His windows cannot be seen through, his doors cannot be opened and the figures produce no element of vitality into the rooms. Hammershoi is defiantly inscrutable; the mood is melancholic and enigmatic, but the paintings are oddly compelling. Quite why, no one seems sure.

Of the 71 paintings in a new exhibition in London, 21 come from his native Copenhagen, 15 from other Scandinavian collections and 20 from private collections, principally Danish. Hammershoi’s focus was not as narrow as this show might suggest, but to see his nudes it is necessary to visit the Statens Museum for Kunst in Denmark. He did some fine, if bleak, landscapes too, but it was the interiors that sold in his lifetime, and he is best remembered for paintings of the sun shining through curtainless window-panes, casting shadows on carpetless floors. 47.Anxious to transform the prosaic into the romantic, his admirers speak of a poet of light and the poetry of silence.

Hammershoi himself was guileless. 48."What makes me choose a motif are the lines, what I like to call the architectural context of an image," he said in 1907. Light was also very important, but it was lines, he insisted, that had the greatest significance for him. His wife, Ida, makes appearances in the empty rooms, but she is usually painted from the back, with the emphasis on the bare nape of her neck. The heroic figures are white doors and windows, and tables, chairs, a piano and a sofa. No painter can have got so much pleasure from painting brown furniture. One work, titled "Interior with a Woman at a Sewing Table", is a symphony of three shades of shiny brown.

Hammershoi was influenced by Vermeer and the 17th-century Dutch genre painters and by Caspar David Friedrich, a German, but there is no one like him. His work shows traces of an unexpected subversive sense of humor. 49.Felix Kramer, the show’s curator, identifies irregularities, for example, that create an almost surreal quality: a piano with two legs, table legs casting shadows in different directions, chests of drawers with no knobs or handles. Even some of Hammershoi’s admirers wonder what it all means.

50.Trying to pin Hammershoi down is as profitless as Waiting for Godot. However, the new exhibition at the Royal Academy of Arts might encourage some excitement in the marketplace. The highest price made by a Hammershoi interior is £ 520,000 ($1 million) in 2006 and the price boom in the auction houses is passing him by. Perhaps the secret of Hammershoi has been kept a bit too well.

49.Felix Kramer, the show’s curator, identifies irregularities, for example, that create an almost surreal quality: a piano with two legs, table legs casting shadows in different directions, chests of drawers with no knobs or handles.

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