71.Nelson Mandela called on the black people to fight for ________(平等的)rights. 72.The Christmas Eve is drawing near. Have you ________(装饰)your Christmas tree? 73.Several companies are________(竞争) for the contract. 74.The train must stop when the________(信号) is red. 75.Eating sweets occasionally doesn't do children any________(危害). 答案:71.equal 72.decorated 73.competing 74.signal 75.harm今天又是化学实验室开放日,老师拿出两瓶无标签的试剂,分别是固体和液体,他取少量试剂在试管中混合,立即产生一种无色气体.我们对此气体展开了一系列探究:Ⅰ探究此气体是什么物质?验证它的实验方案如下:
猜想与假设
实验步骤
现象及结论
此气体可能是二氧化碳二氧化碳
(1)产生此气体的化学方程式可能是CaCO3+2HCl═CaCl2+H2O+CO2↑CaCO3+2HCl═CaCl2+H2O+CO2↑.(2)我想制取该气体,采用的发生装置可选取下图中的BB(填序号).(3)图是收集该气体的装置,气体由aa端(填“a”或“b”)导入.Ⅱ我猜想此无色气体还可能是另外一种气体O2O2(填化学式)