问题 填空题

现有部分常见元素的性质或原子结构如下表:

元素编号元素性质或原子结构
X由它形成的某种单质气体的密度约为空气的1.1倍
Y历史上道尔顿曾用⊙来作为它的元素符号,它的单质是最轻的气体
Z由它组成的某种单质是细鳞片状的很软的固体,有金属光泽和滑腻感
WK层和M层电子数之和等于L层的电子数
(1)元素X和Y能形成原子个数比为1:1的化合物,其化学式为______.

(2)写出元素Z组成的这种单质的一种用途______.

(3)元素W可形成一种单质,其式量为256,该单质的化学式为______.

答案

(1)相同条件下,密度比等于相对分子质量比,X的相对分子质量=1.1×29≈32,故X是氧元素;

Y的单质是最轻的气体,故Y是氢元素;元素X和Y能形成原子个数比为1:1的化合物,其化学式为H2O2

(2)由Z元素组成的某种单质是很软的非金属单质,有金属光泽和滑腻感,故Z元素为碳元素;元素Z组成的这种单质为石墨,它可以做电极等;

(3)W元素K层和M层电子数之和等于L层的电子数,W的原子序数=8+8=16,根据质子数=原子序数,可知W的质子数为16,W元素为硫元素,相对原子质量为32;硫元素形成的一种单质,设该单质的化学式为Sa,其相对分子质量为256,32a=256,故a=8,故该单质的化学式为S8

故答案为:

(1)H2O2

(2)作润滑剂或电极;

(3)S8

单项选择题

Some pessimistic experts feel that the automobile is bound to fall into disuse. They see a day in the not-too-distant future when all autos will be abandoned and allowed to rust. Other authorities, however, think the auto is here to stay. They hold that the car will remain a leading means of travel in the foreseeable future.

The motorcar will undoubtedly change significantly over the next 30 years. It should become smaller, safer, and more economical, and should not be powered by the gasoline engine. The car of the future should be far more pollution-free than present types.

Regardless of its power source, the auto in the future will still be the main problem in urban traffic congestion (拥挤). One proposed solution to this problem is the automated highway system.

When the auto enters the highway system, a retractable (可伸缩的) arm will drop from the auto and make contact with a rail, which is similar to those powering subway trains electrically. Once attached to the rail, the car will become electrically powered from the system, and control of the vehicle will pass to a central computer. The computer will then monitor all of the car’s movements.

The driver will use a telephone to dial instructions about his destination into the system. The computer will calculate the best mute, and reserve space for the car all the way to the correct exit from the highway. The driver will then be free to relax and wait for the buzzer (蜂鸣器) that will warn of his coming exit. It is estimated that an automated highway will be able to handle 10,000 vehicles per hour, compared with the 1,400 to 2,000 vehicles that can be carried by a present-day highway.

What is the author’s attitude toward the future of autos().

A. Enthusiastic.

B. Pessimistic.

C. Optimistic.

D. Cautious.

单项选择题