题目

①实验室在制备氨气前如何检查装置的气密性？简述操作步骤？． ②实验室在用制氢气的简易装置制取氢气前如何检查装置的气密性？简述操作步骤？． 答案：【1】将导管的一端放入水中，用手捂住试管一会儿，若导管口有连续的气泡冒出时，并在导管口形成一高于液面的稳定水柱，则气密性好【2】把玻璃阀门关闭，从球形漏斗中注入水近满待片刻，如果水面不下降，即可以使用．使用前应该在有磨砂口处涂上凡士林，以防漏气阅读下面的短文，从短文后的选项中选出能填入空白处的最佳选项补全短文。选项中有一项为多余选项。Trust (信 任) is the basis (基 础) of any relationship, including friendship. No relationship can be long without trust. But winning trust is not easy as we think. Sometimes, it takes years, even all our life to make it. We surely know who are the people we trust. However, how do we know if others trust us?1.You may first like to share them with the friends you trust most. It is the same with your friends.Whom do you ask for advice when you need it the most? Either your parents or your friends may first come into your mind. You only ask for advice from the people you really trust. You know they will never pass on the wrong advice. And so do they.2.Different ideas and discussions are a part of every relationship, and this is also true for friendship. In fact, two people can’t always have the same opinions on a situation and they may share different advice. Sometimes some people find it hard to forgive (原谅) and forget.3..It is because they trust you and believe that you will never cause any hurt to them on purpose (故意地).There are times in life when you find yourself a lonely soldier.4.Your friends will always be there when you need help. If they are with you when you need them the most, you can know that they trust you.A.Whom would you like to share your secrets with?B.But for your true friends, there is no difficulty in it.C.Their friends will never have different opinions.D.However, if you have true friends, you will never be alone in any trouble.E.The friends who trust you will go to you for help in the important decisions of their life.