The contract is very important for both of you, so studying it ________before signing is necessary. A.in return B.in exchange C.in detail D.in turn 答案:C实验室用加热高锰酸钾的方法制取氧气时,用排水法收集,回答下列问题:
(1)制取氧气前要检查装置的气密性,目的是防止装置________;检验方法是________.
(2)导管伸入制氧气试管里不宜过长,原因是________.
(3)在试管口放一团棉花,其目的是________.
(4)加热时先将酒精灯在试管下方来回移动,其目的是________.
(5)用排水法收集时,当气泡________时,开始收集.
(6)集满氧气的集气瓶应盖好________,________放在实验台上.