问题 问答题

初中化学课学完以后,化学学习兴趣小组对实验室制取气体的原理、用到的仪器、药品、收集方法进行总结,请你作为发言人,填写下面的空白内容:

(1)九年级化学里我们学了在实验室制取氢气、氧气、二氧化碳,这三种气体可以共用一套发生装置,所用仪器为带导管的双孔塞、______、______等三种仪器.

(2)实验室用该套装置制取氧气时所用到的原理是(填化学方程式)______.

(3)制取时采用的化学原理是置换反应的气体是______.

(4)制得的气体为氧化物,则该气体的验满方法是______.

答案

(1)实验室制取氢气、氧气、二氧化碳,这三种气体可以共用一套发生装置,为固体和液体不需加热制取气体的发生装置,所用仪器为带导管的双孔塞、盛装药品的锥形瓶,添加液体的长颈漏斗等;

(2)该套装置属于固体和液体常温反应,不需加热,双氧水制取氧气不需加热,可用此发生装置,方程式是2H2O2

 MnO2 
.
 
 2H2O↑+O2↑;

(3)锌和硫酸反应生成硫酸锌和氢气属于置换反应,过氧化氢分解属于分解反应,碳酸钙和盐酸反应制取二氧化碳属于复分解反应;

(4)氢气、氧气是单质,二氧化碳是氧化物,检验其是否收集满的方法是将燃着的木条放于集气瓶口,观察木条是否熄灭进行判断;

故答案为:(1)锥形瓶;长颈漏斗;

(2)2H2O2

 MnO2 
.
 
 2H2O↑+O2↑;

(3)H2

(4)将燃着的木条放于集气瓶口,若木条熄灭则收集满了.

单项选择题

The differences in living standards around the world are vast In 1993, the average American had an income of about $25,000. In the same year, the average Mexican earned $7,000, and the average Nigerian earned. $1,500. Not surprisingly, this large variation in average income is reflected in various measures of the quality of life. Changes in living standards over time are also large. In the United States, incomes have historically grown about 2 percent per year (after adjusting for changes in the cost of living). At this rate, average income doubles every 35 years. In some countries, economic growth has been even more rapid. In Japan, for instance, average income has doubled in the past 20 years, and in South Korea it has doubled in the past 10 years.

What explains these large differences in living standards among countries and over time The answer is surprisingly simple. Almost all variation in living standards is attributable to differences in countries’ productivity—hat is, the amount of goods and services produced from each hour of a worker’s time. In nations where workers can produce a large quantity of goods and services per unit of time, most people enjoy a high standard of living; in nations where workers are less productive, most people must endure a more meager existence. Similarly, the growth rate of a nation’s productivity determines the growth rate of its average income.

The fundamental relationship between productivity and living standards is simple, but its implications are far-reaching. If productivity is the primary determinant of living standards, other explanations must be of secondary importance. For example, people might think that labor unions or minimum-wage laws contributed to the rise in living standards of American workers over the past century. Yet the real hero of American workers is their rising productivity.

The relationship between productivity and living standards also has great implications for public policy. When thinking about how any policy will affect living standards, the key question is how it will affect our ability to produce goods and services. To improve living standards, policymakers need to raise productivity by ensuring that workers are well educated, have the tools needed to produce goods and services, and have access to the best available technology.

The study of the relationship between productivity and living standards is significant in that ().

A. it calls policymakers’ attention to a qualified work force

B. it encourages workers to get better education

C. it helps improve the workers’ ability to produce goods and services

D. it enables policymakers to access the latest technology

单项选择题