等质量的CuO和MgO粉末分别溶于相同体积的硝酸中，得到的Cu(NO3)2和Mg(NO3)2的物质的量浓度分别为a mol·L-1和b mol·L-1（假设反应前后溶液体积无明显变化），则a与b的关系为
A．a＝b
B．a＝2b
C．2a＝b
D．a＝5b
答案：C
等质量的CuO和MgO粉末物质的量的比为1：2；由铜、镁元素守恒得Cu(NO3)2和Mg(NO3)2的物质的量比为1：2，即其浓度比为1：2，所以得2a＝b；
补全对话（共5小题; 每小题2分, 满分10分） Brad: I went to Adele’s open-air concert yesterday. She is really a great singer. John: You must have been so excited at the concert. Brad: 1 John: Why was that? Brad: The concert was very crowded. We all stood because there were no seats. John: 2 Brad: Unfortunately, right beside my left and my right were two “large” people. I am short and skinny and I was like the meat in between two pieces of bread! Just like a hamburger! John: Poor guy. 3 Brad: Actually, I did. They were shouting and screaming crazily while I was firmly stuck between them, with my feet off the ground! My shoulders were hurt! John: 4 Brad: It’s all right. But what made me surprised was that after the concert, the two giants asked me whether I’d like to grab a cup of coffee. John: Did you go with them? Brad: 5 John: What did you have? Brad: Hamburgers.
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