问题 填空题

多原子分子氰(CN)2、硫氰(SCN)2和(OCN)2的性质与卤素单质(Cl2、Br2等)相似,故称它们为拟卤素。它们可以生成酸和盐(见下表,表中X代表F、Cl、Br或I)。

 卤素硫氰
“单质”X2[(CN)2(SCN)2(OCN)2
HXHCNHOCN
KXKCNKSCNKOCN
 

(1)在表中①②空格处应分别填写_______、_______。

(2)①(CN)2和KOH溶液反应的化学方程式为:__________________________。

②已知阴离子的还原性强弱为:Cl<Br<CN<SCN<I。试写出在NaBr和KSCN的混合溶液中加入(CN)2反应的离子方程式:____________________________________。

答案

(8分)(1)氧氰  HSCN 

(2)① (CN)2+2KOH=KCN+KOCN+H2O   ② (CN)2+2SCN=2CN+ (SCN)2

题目分析:(1)、由氰、硫氰的组成可知,(OCN)2可视为(SCN)2中的S被O取代所得的物质,因此①或(OCN)2的名称为氧氰;由单质与酸的组成可知,②的化学式为HSCN;(2)、①Cl2与KOH的反应式为Cl2+2KOH=KOCl+KCl+H2O(或KClO+KCl+H2O),结合表中盐的组成,由相似性类比可知,(CN)2+2KOH =KOCN+KCN+H2O;阴离子的还原性强弱为:Cl<Br<CN<SCN<I,由氧化还原的强弱规律可知,氧化性强弱顺序为:Cl2>Br2>(CN)2>(SCN)2>I2,由强制弱原理可知,(CN)2不能氧化Br,只能氧化强还原性的SCN,则反应式为(CN)2+2KSCN=2KCN+(SCN)2,离子方程式为(CN)2+2SCN=2CN+ (SCN)2

阅读理解

C

  The curtain on the 2008 US presidential election finally rose last month as Requblican Senator(参议员) John McCain and Democratic Senator Barack Obama were formally selected as candidates of the two major parties.This may be one of the hardest decisions voters have to make between two appealing candidates.The big question for voters,as they face both an economic downturn and international threats,is :who will they elect? A young first - term senator promising change and new ideas,or a longtime senator with strong military experience and a reputation as a maverick(特立独行的人)?

  American voters have never seen a candidate quite like Obama.He has a white mother from the US and a black fater from Kenya who left the family when Obama was very young.He spent part of his youth in Indonesia.

  However,McCain has a very different life story.

  He grew up in a Navy family and was a daring pilot during the Vietnam War in the 1960s. When Obama was in kindergarten in Indonesia,McCain's plane was shot down over Ietenam and he became a prisoner of war.McCain could have been set free if he disowned America but he refused and so was held for five years.

  "We need a president who is very,very old,"McCain joked at his age as many others do.If elected,he would be 72 when he takes office and the oldest man to step in.

  So in the end,the election may depend on several factors that are hard to judge:Will Obama's race matter to a significant number of voters ? Will workingclass whites who tended to support his primary (党内初选) oponent,Hillary Clinton,vote for Obama? And perhaps most important of all,will uncertain voters be more attracted to Obama's vision or to McCain's experience?

  Whatever happens,one thing is clear,however:Whoever walks into the White House on January 20,2009,will find huge challenges waiting for him in the Oval Office,both at home and abroad.

  64.______makes the result of the election hard to predict.

   A.Whether working class whites care about Obama's inexperience

   B.The economic trouble the country now faces

   C.Who uncertain voters will finally decide to vote for

   D.McCain being too old to govern the country

  65.The appeal in Obama as a presidential candidate lies in _________

   A.his multi - cultural background

   B.his belife in tradition

   C.his inexperience in politics

   D.his fantastic promises

  66.The word "disown" in Paragraph 6 means closest to ______.

   A.flee from

   B.turn his back on

   C.not keep it private

   D.expose secrets about

  67.The challenges that will face the new preident______.

   A.are not mentioned in the text

   B.include buklding a strong party and a friendly image

   C.refer to the problems of immigrants and economy

   D.refer to the problems of economy amd international relations

单项选择题