题目

Without plants, people couldn’t live. We eat plants. _____36____. And we need plants for another reason: We need them because they are beautiful. _____37_____.Imagine no flowers with their sweet smells, their beautiful colours and their lovely shapes. Imagine, when the wind blows, we are not able to hear the leaves of the trees or watch the branches swing from side to side. _____38____.That is why we have parks full of trees and flowers. That is why people always like houses with room for some grass and a garden. Do you talk to your plants?  _____39___Perter Tompkins and Christophe5．某化学兴趣小组的同学学习“灭火器原理”后，设计了如图所示实验，并对反应后瓶中残留废液进行探究．【提出问题】废液中所含溶质是什么？【猜想与假设】猜想1：废液中的溶质可能是NaCl、Na2CO3和HCl．猜想2：废液中的溶质只有氯化钠（填名称）．猜想3：废液中的溶质是NaCl和HCl．猜想4：废液中的溶质是NaCl、Na2CO3．【讨论与交流】小明认为猜想1无需验证就知道是错误的，他的理由是在溶液中Na2CO3和HCl不能共存．【实验与结论】（1）为验证猜想2，小强同学取少量废液装入试管中，然后滴入AgNO3溶液，产生白色沉淀，滴加稀硝酸沉淀不溶解．于是小强认为猜想2正确．小强的实验不能（填“能”或“不能”）验证猜想2的正确性，原因是稀盐酸能与硝酸银生成了不溶于稀硝酸的白色沉淀．（2）小丽为验证猜想3，选用碳酸钠做试剂．若猜想3是正确的，验证时反应的化学方程式为Na2CO3+2HCl═2NaCl+H2O+CO2↑．（3）若验证猜想4是否正确，下列试剂中可选用的有②③（填序号）．①氢氧化钠溶液   ②氯化钙溶液   ③稀盐酸   ④氯化钾溶液．