问题 单项选择题

用司盘20(HLB=8.6)和吐温60(HLB=14.9)组成的混合表面活性剂的HLB值为12.38,问二者混合量之比是

A.2:5

B.3:2

C.3:4

D.4:3

E.2:3

答案

参考答案:E

解析:
掌握混合表面活性剂的HLB值的计算。
解:非离子型表面活性剂的HLB值具有加和性,其混合体系的HLB值可用下式计算:
HLBab=(HLBa·Wa+HLBb·Wb)/(Wa+Wb)
式中:HLBab为混合乳化剂的HLB值;
HLBa为乳化剂a的HLB值;Wa为乳化剂a的重量;
HLBb为乳化剂b的HLB值;Wb为乳化剂b的重量。
将数据代入公式:12.38=[8.6×Wa+14.9×(1-Wa)]
计算得:Wa:Wb=2:3

填空题
Fill in the blanks with the right form of the proper words in the box. Each word should be used only once.
take, million, cook, science, south, grow, many, probably, know, nothing
       People all over the world eat rice. 1.              of people in Asia, Africa and South America eat it every
day of their lives. Some people eat almost 2.              but rice. 
       Rice is a kind of grass. There are 3.             than 7,000 kinds of rice. Farmers grow rice in many
countries, even in the 4.              part of the United States and in eastern Australia. 
       No one really 5.              where rice came from. Some 6.              think that it started to grow in two
places. They think that one kind of rice grew in southern Asia thousands of years ago. Someone in China
wrote about it almost 5,000 years ago. Another kind 7.              grew in West Africa. Other scientists think
that rice came from India, and Indian travelers 8.              it to other parts of the world.
       There are two main ways 9.              rice. Most rice grows in west soil. People in many countries do all
of the work of growing rice by hand. This is the same way farmers worked hundreds of years ago. In some
countries, people now use machines on their rice farms.
        People use every part of the rice plant. They make animal feed and rice oil from it. They burn dry rice
plants for 10.             .
单项选择题