问题 问答题

重量分析法的特点是什么

答案

参考答案:重量分析法通常是用适当的方法将被测组分与试液中的其他组分分离,然后转化为一定的形式,用称量质量的方法测定该组分的含量。
由于重量分析法直接用分析天平称量而获得分析结果,无需与基准物质相比较,如果分析方法可靠,操作细心,可以获得准确的结果。但是,重量分析须经沉淀、过滤、洗涤、灼烧和称量等手续,操作烦琐,费时较多。一般来说,若有其他方法可以代替,尽量避免使用重量分析法。

阅读理解

At least 10 million hectares of cultivated(耕作)land in China are polluted, which makes a grave threat to the country’s food safety, the Xinhua News Agency reported on Friday.

The polluted land,which is mostly in economically developed areas,accounts for one-tenth of the country’s total arable(可耕种的)land,according to an incomplete survey by the State Environmental Protection Administration,China’s top environment watchdog.

Pollution on cultivated land threatens the environment,food safety and the sustainable development of agriculture,the administration said.

Because of continual,too much use of chemical fertilizer, pesticide and agricultural plastic sheeting, as well as irrigation using polluted water, a large amount of contaminants(污染物)remain in the cultivated land.

The contaminants affect the soil’s ecological structure and function,leading to decreased soil productivity, lower crop yield(产量),and lower quality of agricultural products-

It also leads to worse water quality in rural areas.

Less than 9 per cent of drinkable water passed checks for bacteria in243 rural water supply stations across the county.

Another survey, which took samples of drinking water and groundwater an 69 small towns。 in Beijing, Tianjin and Hebei Province of North,China, showed that more than half of the water contains too much nitrate(硝酸盐),which may cause diabetes(糖尿病)and damage the kidney.

The administration estimated at least 1 90 million farmers are drinking water that contains harmful substances.

Many villagers drink unfiltered water taken from shallow water wells or water cellars, which are reported to have poor sanitary conditions·

小题1:The author writes the passage to            .

A.1et the readers examine their mistakes

B.present the readers a new idea

C.come up with a solution to ending farmland pollution

D.inform the readers of the importance of fighting farmland pollution小题2:The underlined word “grave” in Paragraph 1 probably means

A.serious

B.certain

C.big

D.terrible小题3:Pollution on cultivated land leads to the following outcomes EXCEPT       .

A.a threat to China’s food safety

B.worse water quality in rural areas

C.a variety of diseases

D.the sustainable development of agriculture

单项选择题