地网施工中焊接部位,以及从室外联合地网引入室内的接地扁钢应作()层防腐处理。
A.一
B.二
C.三
D.四
参考答案:C
(1)已知含11.2g KOH的稀溶液与1L0.1mol•L-1的H2SO4稀溶液反应放出11.46KJ的热量.请写出KOH的稀溶液与的H2SO4稀溶液发生中和反应,表示中和热的热化学方程式为______
(2)在相同条件下,下列两个反应的反应热分别为△H1和△H2表示:
①2H2 (g)+O2(g)=2H2O(g)△H1,
②2H2 (g)+O2(g)=2H2O(l)△H2,则△H1和△H2的关系为______.
The United States counts its population every ten years, and each census reveals that the racial and ethnic mix is changing dramatically, so by the year 2050, the "average" American will not be descended from (1) , but the majority of U. S. residents will trace (2) ancestry to Africa, Asia, the Hispanic world, the Pacific Islands, or the Middle East. Once the United States was a microcosm of European nationalities, (3) the United States is a microcosm of the world. The United States is (4) considered a "melting pot" society by many of its residents. (5) , many people prefer the term "salad bowl." They use this (6) to describe American society. American society will soon be (7) nonwhite. "Melting pot" implies that the different ethnic groups blend together (8) one homogeneous (9) , "salad bowl" (10) that nationalities, like the ingredients in a mixed green salad, retain their cultural (11) . Earlier generations of (12) believed they had to learn English quickly not only to survive but also for (13) . Now, many immigrant groups do not (14) the same need. Because there are many places in America (15) you can work, shop, get medical care, marry, divorce and die without knowing English. (16) , Chinatown in San Francisco and New York. Also, Los Angeles has many Vietnamese immigrants and immigrants from Mexico. (17) , many immigrant groups want their children to know their (18) culture. Many Hispanics, for instance, want their children to learn (19) English and Spanish and study the Spanish language in school. They are fighting for the (20) to bilingual education in many communities. In many communities they are in the majority.