问答题简答题：辨析题：简述碳酸钠（Na2CO3）的作用机理。

题目：

辨析题：简述碳酸钠（Na₂CO₃）的作用机理。

答案：

参考答案：

碳酸钠又叫苏打。它在矿浆中解离产生OH^-、HCO₃^-及CO₃²^-等离子。HCO₃^-为弱酸性，OH^-为强碱性（但OH^-浓度小），一般调整矿浆的PH值范围在8～10左右。其优点是矿浆的PH值比较稳定，有一定的缓冲作用，也不存在Ca²⁺的副作用。在用脂肪酸作捕收剂浮选非硫化矿物时，常用碳酸钠做PH调整剂，它可沉淀矿浆中的Ca²⁺、Mg²⁺等有害离子，降低脂肪酸的消耗量。碳酸钠可作黄铁矿的活化剂。有清洗表面的作用。碳酸钠还可与硅酸纳等其它抑制剂配合使用，可调节抑制作用的强度。它还能分散矿泥，是一种良好的分散剂。

题型：阅读理解

Mobile phones are an important business tool for farmers in rural areas. But they also put a valuable educational tool in their hands.

The University of Illinois in the United States has a project called SAWBO—Scientific Animations Without Borders. It produces educational videos that can be downloaded to cell phones. The goal is to help people in developing countries improve their lives.

One video shows farmers how to make a natural insecticide from neem seeds to prevent insect damage to crops. The process starts with sorting and drying the neem fruits. Then let the fruit dry in the sun for about three or four days, until they become brown. Using a mortar(碾槌) and stick, the fruits are slightly pounded to remove the shells from the fruits without breaking the seed inside.

The videos use computer animation(动画). Some of the animated characters are a little funny looking-like a farmer with a long nose. But the subjects are serious, including a health video on preventing cholera(霍乱). Team member Francisco Seufferheld says the information in the videos is meant to be quickly understood. He says, “The information is digested in such a way that in two minutes, we can transmit a complex idea.”

The researchers tested the seven-minute video on seven mobile phones. They wanted to see if people would share the video using Bluetooth wireless technology. With Bluetooth, files can be passed to a nearby phone even if neither phone is connected to the Internet. As a result, in one month, the video had spread to one hundred eighteen people in fifty different villages. “This is just incredible impact,” said Francisco Seufferheld.

The team has made a few videos so far. These are available in a total of eighty languages, dialects and accents. Professor Barry Pittendrigh says there are plans for more videos later this year.

小题1:What is the text mainly about?

A．A best-selling mobile phone

B．A valuable educational project for farmers

C．United States support for developing countries

D．A new type of scientist –farmer relationship小题2:The SAWBO program is introduced in order to ____.

A．raise farmers’ standard of living

B．do some research on mobile phones

C．develop farmers’ practical skills

D．help farmers prevent insect damage to corps小题3:The biggest advantage of the program is that it______.

A．includes health video on preventing cholera

B．can be passed to farmers using Bluetooth technology

C．can be used to sort and dry the neem fruits

D．is easy for farmers to understand小题4:Which of the following words can best take the place of the word “ pound” in the 3^rd paragraph?

A．moved

B．beat

C．picked

D．cut

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