A、B、C、D是四种可溶的化合物，分别由阳离子K+、Ba2+、Al3+、Fe3+和阴离子OH-、CO32-、NO3-、
SO42-两两组合而成，它们的溶液发生如下反应：A与B反应生成白色沉淀，再加过量A，沉淀量减少，但不会完全消失。C与D反应生成有色沉淀。B与C反应生成白色沉淀。
写出它们的化学式：A：________，B：________，C：________，D：________。
Ba(OH)2；Al2(SO4)3；K2CO3；Fe(NO3)3
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| When I was thirteen, my family moved from Boston to Tucson, Arizona. 1 the move, my father 2 us in the living-room on a freezing January night. My sisters and I sat around the fire, not 3 that the universe would suddenly change its course. "In May, we' re 4 to Arizona." The words, so small, didn't seem 5 enough to hold my new life. But the world changed and I awoke on a tram moving across the country.1 watched the 6 change from green trees to flat dusty plains to high mountains as I saw strange new plants that 7 mysteries yet to come. Finally, we arrived and 8 into our new home. 9 my older sisters were sad at the loss of friends, I 10 explored our new surroundings. One afternoon, I was out exploring 11 and saw a new kind of cactus(仙人掌). I crouched(蹲) down for a closer look. "You'd better not 12 that" I turned around to see an old woman. "Are you new to this neighborhood?" I explained that I was, 13 , new to the entire state． "My name is Ina Thorne." Have you got used to life in the 14 ? It must be quite a 15 after living in Boston." How could I explain how I 16 the desert? I couldn't seem to find the right words. "It's vastness," she offered. "That vastness 17 you stand on the mountains overlooking the desert-you can 18 how little you are in comparison with the world. 19 , you feel that the possibilities are limitless." That was it. That was the feeling I'd had ever since I'd first seen the mountains of my new home. Again, my 20 would change with just a few simple words. "Would you like to come to my home tomorrow?" Someone should teach you which plant you should and shouldn't touch." | ||||
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