由海水制备无水氯化镁，主要有以下步骤：①在一定条件下脱水干燥_爱下问搜题

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问题选择题

由海水制备无水氯化镁，主要有以下步骤：①在一定条件下脱水干燥；②加熟石灰；③加盐酸；④过滤；⑤浓缩结晶。其先后顺序正确的是（　　）。

A．②④⑤③①

B．③②④①⑤

C．③④②⑤①

D．②④③⑤①

答案

答案：D

本题是由海水制备无水氯化镁，主要步骤是先将海水中的氯化镁成分转变为氢氧化镁即②步为第一步骤，④过滤，得到氢氧化镁，再用③加盐酸的方法，将其变为氯化镁溶液，⑤浓缩结晶，①在一定条件下脱水干燥即可得到无水氯化镁。

选择题

N_A表示阿伏加德罗常数，下列说法正确的是

A．标准状况下，等体积的水和CO₂，含有的氧原子数目为1∶2

B．含有N_A个阴离子的Na₂O₂与足量水反应，转移电子数为2N_A

C．向FeI₂溶液中通入适量氯气，当有N_A个Fe²⁺被氧化时，共转移电子数为3N_A

D．一个NO分子质量为a g，一个NO₂分子质量是b g，则N_A个O₂的质量为（b—a）N_Ag

完形填空

Alone in the light at the dining room table, surrounded by a nearly dark house, I sat in tears.
Finally, I 36 in getting both kids to bed. As a new single 37 , I had to be both Mommy and Daddy to my two little children.
With full rights of my children, I 38 to give them a normal and comfortable home life. I 39 a happy face for them.
I rose slowly, trying not to 40 even the least sound which might start them up 41 . I tiptoed(蹑手蹑脚地走) out of their room, 42 the door part way, and went downstairs.
And loneliness(孤独). I 43 as thought I were at the bottom(底部) of a great sea of loneliness. It all 44 together and I was at once lost. I sat there, 45 crying.
Just then, a pair of little 46 went around my middle and a little face looked up at me. I looked down into my five-year-old son’s 47 face.
I was shy to be 48 crying by my son. “I’m sorry. Ethan, I didn’t know you were stillo awake.” I don’t know why, but so many people 49 when they cry and I was no exception. “I didn’t 50 to cry. I’m just a little 51 tonight.”
“It’s okay, Daddy. It’s okay to cry; you’re just 52 .”
I couldn’t express(表达) how happy he made me, this little boy, who was simple, gave me 53 to cry. He seemed to be saying that I didn’t have to always be 54 , and that sometimes it was possible to allow myself to feel weak and let out my 55 .

A．experienced