题干

设阿伏加德罗常数的值为NA,则下列说法中正确的是(  )

A:加热条件下,1mol Cl2与足量Fe粉充分反应,转移的电子数为3NA

B:常温常压下,14g N2所含的原子数目为NA

C:常温下,1mol/L (NH4)2SO4溶液中含SO42数为NA

D:标准状况下,2.24L H2O中含有的电子数为NA

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答案(点此获取答案解析)

B

同类题4

阅读下面短文, 从短文后各题所给的四个选项(A、B、C、D)中, 选出可以填入空白处的最佳选项。
     “Paul must have been trying to carry his waste paper to garbage can and dropped a few pieces.” I1picking them up. 2later I found more pieces. No quiet sighing this time. I 3 ,“Who is throwing garbage?” No answer. Instead, I saw more bits of paper silently floating 4 from upstairs. Looking up, I saw my seven-year-old son, Paul.
     “Stop making a mess.” “It's not a mess. They're5.” “Sorry, what did you say?” I hadn't heard him clearly.
    He didn't answer me. Paul has autism (自闭症) and6answers a question, especially when he's7attentively on something else. He ran down the stairs. “Where are my other butterflies?” he asked,8around. Every time Paul 9five or more words together, my heart says a 10of thanks. But lately he seems to 11that the benefits of forming complete sentences when communicating are12of the effort.
    Butterflies. Of course. I rushed to13them from the garbage,14them off and handed them to my young artist. “Want to see them15again?” he asked with a shy smile. “Oh yes! They're beautiful.” I whispered. He ran back upstairs to float his16 down again. They really did look like beautiful butterflies.
    That day Paul 17me to look up at 18instead of down at garbage. How many other masterpieces (杰作) do I miss because I'm too caught up in my 19to take time to appreciate what's right in front of me? Life is not what happens to us. It's 20 we look at it. Now, I look up.