问题 填空题

(7分)铬(Cr)为不锈钢主要的添加元素,含量一般在12%以上。铬的表面生成一薄层致密的钝态氧化物保护膜是不锈钢具有耐蚀性主要原因。请回答下列问题:

(1) 铁生锈的主要条件是铁与________和________直接接触。

(2) 不锈钢是一种____________(填“合金”或“金属”)。

(3) 相同温度下,取大小相同、表面光亮的Cr、Mg、Cu三种金属薄片,分别投入等体积等溶质质量分数的足量稀盐酸中(反应中Cr显+2价),现象如下:

金属CrMgCu
与盐酸反应现象放出气泡速率缓慢放出气泡速率较快无明显现象
① 上述三种金属的活动性由强到弱的顺序是__________________。

② 从上述探究实验可知,Cr ______(填“能”或“不能”)跟硫酸铜溶液反应。若反应,请写出反应的化学方程式______________________             ________。

答案

(1)O2、H2O(每空1分,方程式2分)

(2)合金

(3)①Mg>Cr>Cu  ②能  ③Cr+CuSO4=CrSO4+Cu

题目分析:1、铁生锈的主要条件是铁与O2和H2O直接接触所致;

2、不锈钢是一种合金;

3、Mg与盐酸反应速度快,Cr与盐酸反应较慢,而铜与盐酸不反应,故上述三种金属的活动性由强到弱的顺序是Mg>Cr>Cu;

4、因Cr的金属活动性比铜强,故Cr能与硫酸铜溶液反应,反应的化学方程式为:Cr+CuSO4=CrSO4+Cu。

点评:铁生锈是铁与O2和H2O反应的结果;常见金属活动性顺序应熟记;书写化学方程式时要注意配平和条件。

单项选择题
单项选择题

It is all very well to blame traffic jams, the cost of petrol and the quick pace of modern life, but manners on the roads are becoming horrible. Everybody knows that the nicest men become monsters behind the wheel. It is all very well, again to have a tiger in the bank, but to have one in the driver’s seat is another matter altogether. You might tolerate the rude and inconsiderate driver, but nowadays the well-mannered motorist is the exception to the rule. Perhaps the situation calls for a "Be Kind to Other Drivers" campaign, otherwise it may get completely out of hand.

Road politeness is not only good manners, but good sense too. It takes the most cool-headed and good-tempered drivers to resist the temptation to revenge then subjected to uncivilized behavior. On the other hand, a little politeness goes a long way towards relieving the tensions of driving. A friendly nod or a wave of acknowledgement in response to an act of politeness helps to create an atmosphere of goodwill and tolerance so necessary in modern traffic conditions. But such acknowledgements of politeness are all too rare today. Many drivers nowadays don’t even seem able to recognize politeness when they see it.

However, improper politeness can also be dangerous. Typical examples are the driver who brakes violently to allow a car to emerge from a side street at some hazard to following traffic, when a few seconds later the road would be clear anyway; or the man who waves a child across a zebra crossing into the path of oncoming vehicles that may be unable to stop in time. The same goes for encouraging old ladies to cross the road wherever and whenever they want to.

A veteran driver, whose manners are faultless, told me it would help if motorists learnt to filter correctly into traffic streams one at a time without causing the total blockages (堵塞) that give rise to bad temper. Unfortunately, modern motorists can’t even learn to drive, let alone be well-mannered on the road. Years ago the experts warned us that the car-ownership explosion would demand a lot more give-and-take from all road users. It is high time for us to take this message to heart.

By "good sense" (Para. 2), the author means ().

A. the driver’s ability to understand and react reasonably

B. the driver’s prompt response to difficult and severe conditions

C. the driver’s tolerance of rude or even savage behavior

D. the driver’s acknowledgement of politeness and regulations