问题 问答题

实验室可用氯酸钾或过氧化氢制取氧气。

过氧化氢的分解的变化可用下式表示:

过氧化氢水+氧气 

上述变化所涉及的物质中,属于金属氧化物的是              ,氧元素的化合价为—1价的是               

用氯酸钾或过氧化氢制取氧气的实验中,都需要加入少量二氧化锰,二氧化锰的作用是           ;若未加入二氧化锰,则反应         (选填“不能发生”或“明显减慢”) 

若实验室要制取48g氧气,至少需要氯酸钾多少克?

答案

(1)二氧化锰(或MnO2)(1分)     过氧化氢(或H2O2)(1分)

(2)加快反应速率(或催化作用)(1分) 明显减慢(1分)

(3)解:设需要KClO3的质量为x。                                    (0.5分)

2KClO32KCl  +   3O2↑                                       (1分)

245           96                                   (2分)

x              48g

=                                                (1分)

x=122.5g                                            (1分)

答:至少需要氯酸钾的质量为122.5g。

(1)金属氧化物是指由金属元素与氧元素形成的氧化物。二氧化锰中是锰、氧两种元素的化合物,属于金属氧化物。

根据化学式可计算出:在反应中的四种物质H2O2、MnO2、H2O、O2中,氧元素的化合价依次为-1、-2、-2、0。

(2)在加热氯酸钾和二氧化锰的混合物制氧气中,二氧化锰作催化剂,起催化作用;

在用过氧化氢和二氧化锰制取氧气的实验中,二氧化锰作催化剂,起催化作用。二氧化锰在两个实验中都起到了加快反应速率的作用。

催化剂的作用是改变化学反应的速率,本身的质量和化学性质在反应并未改变。所以在这两个反应中如不加入二氧化锰反应也可发生,只是速度要比加二氧化锰明显减慢。

(3)解题思路:已知氧气的质量为48g,求需要氯酸钾的质量。可根据用氯酸钾制氧气的反应中二者的质量关系进行计算。具体解题过程:

解:设需要KClO3的质量为x。                 设未知量

2KClO32KCl  +   3O2↑               写出反应的化学方程式

245                 96                找出氯酸钾与氧气的质量比

x                 48g               标出二者在反应中实际质量比

=                            根据标出数值列比例式

x=122.5g                     求解未知量

答:至少需要氯酸钾的质量为122.5g。          写出答案

点评:本题结合氧气的制取方法考查了金属氧化物、催化作用、化合价、根据化学方程式的计算,可根据相关知识点进行解答。

阅读理解

Ⅲ 阅读 (共两节,满分40分)

第一节阅读理解(共15小题;每小题2分,满分30分)

阅读下列短文,从每题所给的A、B、C和D项中,选出最佳选项,并存答题卡上将该

项涂黑。

(A)

Increasingly over the last few years,we have become familiar with the range of small electronic devices or  “smart” accessories (附件,饰品 ) . Pocket heart -rate monitors for joggers and electronic maps are just the first examples of many new products that promise to change our lives in all sorts of surprising ways.

As a scientist at New York University . Rosalind Picard tries out different smart accessories before they go on the market.  One of these was the so-called " frown (皱眉)headband". Rosalind was shocked to realize just how often she frowned. Stuck in a traffic jam recently, Rosalind kept hearing the sounds of the tiny sensor inside the band worn around her forehead -each time she frowned in annoyance, the sensor gave out a signal.

Another computer scientist , Stevcn Feiner, is working on a pair of glasses that will do more than help you to see .Imagine you want to try a restaurant in a foreign city but you're not familiar with the dishes on the menu.  If you are weanng a pair of Steven's glasses . all yau have to do is glance above the restauran’s doorway and your glasses will immediately become windows to the Tntemet, offering you full details of the meals served inside. The glasses could also be used to help people make speeches,give chefs access to the latest recipes and even provide doctors with

patient information while they carry out operations.

At the moment, Steven's invention looks more like a large ski mask than a pair of glasses.

It's a headset connected to a hand-held computer and a Global Positioning  System  ( GPS ) receiver, which tracks the wearer's position. But he says that these head-worn displays will eventually get smaller and lighter as technology improves.

And, of course, this new technology has a fashionable as well as a useful application. A chemical engineer named Roben Langer has invented a new microchip that, if put inside a ring,can give off different smells according to a person's mood. That, of course, may or may not appeal to you.  And,in the end , it is  shoppers . not scientiscs , who will determine which of these smart accessories will succeed as fashionable items and which are sure tO join history's long list of crazy inventions.

It is clear,however ,that as computers get smaller and cheapcr.  Lhcy will pop up in all sorts

of easily-wearable accessories . even in the buttons on your coat.  WhaCs morc, this is something that's going to happen a lot sooner than we all expect.

41. When Rosalind wore the headband, she was surprised a___________

A. how well the sensor worked           B. how she was affected by traffic

C. how strong the signal was            D. how uncomfortable it was

42.  For people eating out , Steven’ s glasses can___________      

A . give them a restaurant's location

B.  let them see a restaurant's environment

C.  inform them about a restaurant’s menu 

D.  tell them about a restaurant's quality

43. What is the current problem with Stevcn's glasses?

A. Limited function.                B. Inconvenience.

C. High cost.                       D. Poor Internet access.

44.  In general, what does the writer think about smart accessories?

A. They will soon be widely available.

B. Much more research is needed into them.

C. Only a few of them will appeal to shoppers.

D. Most of them are considered to be crazy inventions.

45. What's the writer's purpose in writing this passage?

A. To advertise some smart accessories.

B .To tell interesting stories about smart accessories.

C. To argue that smart accessories are fashionable.

D. To introduce the idea of smart accessories.

选择题