搜题请搜索小程序“爱下问搜题”
问题 选择题

已知阿伏加德罗常数近似为6.02×1023mol-1。下列叙述正确的是  [ ]

A．15g甲基（CH3-）中含有电子的数目为10×6.02×1023

B．42g乙烯与丙烯的混合气体中含碳原子数为3×6.02×1023

C．标准状况下，22.4L己烷中碳碳键数目为5×6.02×1023

D．乙烯和乙醇的混合物共0.1mol，完全燃烧所消耗的氧分子数一定为0.6×6.02×1023

答案

答案：B

单项选择题

在容器内工作时的安全电压为（）V。

A.12

B.6

C.24

D.36
查看答案
单项选择题

Many immigrants to the United States find the decision to seek better lives for their families in America can have an unexpected and tragic consequence. Deep differences with their children develop over language and culture.
"Many immigrants arrive here without much education. Their kids soon gain language skills and also street marts on how to live in America, leaving the parents at a disadvantage, " Ileana, Roses, pastor of a Methodist church group operating in Virginia, said.
"Not only that but they find they cannot relate to children who quickly absorb American culture, " she said.
According to the US Census Bureau, the number of foreign born or first generation Americans reached 55 million last year, a record one in five of the total population.
A government survey of 922 immigrants in 2000 found that nearly 40 percent of those who had been in the United States for more than 15 years would still like to take English classes if they had the time.
Two thirds of low income households depended on their children for translation.
Psychologists and sociologists say parents can lose their position of authority in a family as a result and the effects of that can be far-reaching.
Children exposed to American pop culture that glorifies youth and sexuality often rebel when their parents try to impose the conservative values they brought with them.
"Americanization erodes all important aspects of parenting, " said Richard Weissbourd, who teaches education at Harvard University.
"I feel a part of me is dying with my children. They don’t listen to my music. I have to play it on Sunday morning when they are not around, " said an immigrant.

From the passage we can infer that the population of the states at present is about ______.

A. 275 million


B. 220 million
C. 255 million


D. smaller than 250 million
查看答案