题干

有一包NaCl的固体,其中可能含有Na2CO3、CaCO3、CuSO4(无水)中的一种或两种.某化学兴趣小组的同学欲探究该固体中的成分和测定其中NaCl的质量分数,请你分析并回答下列问题:

Ⅰ.探究该固体的成分.如下图:

根据以上实验可知:

上一题 下一题 0.0难度 选择题 更新时间:2013-05-27 02:59:59

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同类题2

下边图表从哲学上启示我们                                          
时间
发明产品
转化为现实生产力所需的时间
二战前
照相机
112年
电动机
65年
电话
56年
二战后
原子能
15年
电视
5年
激光
2年

同类题3

    As a music teacher for twenty-seven years I have always known that music touches the soul. It can break through all kinds of barriers to reach students in a very special way. It can be the means for each child to find their light.
    A few years ago I was blessed with the opportunity to teach pre-school students one afternoon a week. One of my most memorable students was Vanessa. She was five years old, had difficulty walking and could not speak. We mostly sat on the floor for our music lessons and Vanessa liked to sit on my lap. One of her favorite songs was John the Rabbit. It was a call and response song where I sang the call and the students clapped two times while singing the repeating phrase “Oh yes!” Vanessa liked to put her hands together with mine and clap with me. We performed that song during every class Vanessa and I clapped together. She never said or sang a word.
    One day late in the school year when the song was finished Vanessa turned around, looked at me in the eye, clapped her tiny hands two times and said the words “Oh yes!” I opened my mouth and could not speak. Through music we had made a connection.
    Several years later I came across Vanessa on the street in town. I stopped my car and waved to say hello. She waved back with a big smile on her face and then clapped her hands two times mimicking the song we had performed in our music class. This precious little girl through her connection with music left an impression on me that will last forever.
    Every child has the ability to learn and grow. It is up to us educators to discover the way to reach each and every one of our students. We all must find each child’s light.