问题 计算题

充分燃烧一定量的乙烯与常温下呈气态的某烃混合气体后,测得其生成物中气体的质量是反应前混合烃质量的2.86倍,试通过计算确定该气态烃的分子式及它在该混合烃气体中所占的物质的量分数(气体质量为常温下所得)。

答案

CH4;81.82%

阅读理解

根据短文内容,回答下列问题。

     Most new babies were born in the developing countries. These countries are found in Africa, South America

and parts of Asia. In the developed countries of Europe and North America, the population is growing very

slowly. This is because women in these countries have, on average (平均), only one or two children. In the

developing countries, many women have five or more children. In 1950, about one quarter of the world's

population lived in the developed countries. By 2050, these countries will be home to only about one tenth of the

world's people.

     In the developing countries, more than one billion people are still living below the poverty (贫困) line. These

people do not have enough food to eat and they live in poor housing conditions. Children get little time at school

and suffer (遭受痛苦) from many kinds of diseases.

     At the beginning of the 21st century, the world's population was around six billion. The U.N. has said that the

world's population will level off (平稳下降) at 12.5 billion by the year 2100. Other groups think the world's

population will continue to grow, reaching 14 billion before it becomes stable (稳定的), or even falls. 

1. In what areas of the world can developing countries be found?

   ________________________________________________

2. In 1950, what percent of the world's population lived in developing countries?

   ________________________________________________

3. How to describe the people who are living below the poverty line?

   ________________________________________________

4. There will be twelve and a half billion people on the earth in 2100, won't there?

   ________________________________________________

5. 将文中画线部分翻译成汉语。

   ________________________________________________

解答题