题干

A、B两种固体物质的溶解度曲线如图所示.请回答:

(1)  ____ ℃时,A、B两种物质的溶解度相同;

(2)我国有些地区有一种说法:“冬天捞碱,夏天晒盐”.这里的碱指Na2CO3,盐是指NaCl.那么,图中  ____ (填A或B)的溶解度曲线与Na2CO3的溶解度曲线相似;

(3)人们用上述方法从盐湖中捞得的Na2CO3(常含有少量的NaCl).试计算Na2CO3的摩尔质量为  ____ ,2mol Na2CO3中约含有  ____ 个碳原子;

(4)某研究性学习小组对捞得的碱进行分析,称取Na2CO3固体(含有少量的NaCl)样品12.5g,将其配制成溶液,再向其中逐滴加入足量的稀盐酸,使气体完全放出,共收集到0.1molCO2气体.该反应的化学方程式为  ____,上述样品中含Na2CO3的物质的量为  ____,质量为 ____

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答案(点此获取答案解析)

t2,A,106g/mol,1.204×1024,2HCl+Na2CO3═2NaCl+H2O+CO2↑,0.1mol,10.6 g

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    In a class this past December, after I wrote some directions on the board for students about their final examination, one young woman quickly took a picture of the board using her smart phone. When I looked in her direction, she apologized, “Sorry. Was it wrong to take a picture?”
    “I can't read my own handwriting,” the young woman explained. “It's best if I take a picture of your writing so I can understand the notes.”
    That remark started a class-wide discussion about taking a picture instead of taking notes. For those in the photo-taking camp, reasons extended(扩展) beyond their inability to comprehend their own handwriting. Some took pictures of notes because they knew their phone was a safe place to store material. They might lose paper, but they wouldn't lose their phones. Some took photos because they wanted to record exactly the way in which I had noted information on the board. Others told me that during class they liked to be able to listen to the discussion attentively.
    Yet the use of cameras may be convenient, it does raise questions for the classroom. Is a picture an effective replacement for the process of note-taking?
    Teachers encourage students to take notes because the act of doing so is more than just recording necessary information—it helps prepare the way for understanding. Encouraging students to take notes may be an old-fashioned method, but just because a method has a long history doesn't mean it's out of date. Writing things down engages a student's brain in listening, visual, and kinesthetic(触觉的) learning. The act of writing down information enables a person to begin to memorize, to process and combine it, helping learning new knowledge.
    Taking a picture does indeed record the information, but it lacks some of the necessary mental activities that taking notes employs. So can the two be equally effective?