题干

某澄清溶液可能含有K+、Al3+、Mg2+、NH4+、Fe2+、Fe3+、Cu2+、SO42-、CO32-中的一种或几种,为确定其成分,进行如下实验:①取部分溶液,逐滴滴入用HCl酸化的BaCl2溶液,产生白色沉淀;②另取部分溶液,缓慢加入足量的Na2O2固体并加热,产生无色无味的气体,同时产生白色沉淀后白色沉淀部分溶解。下列推断正确的是(   )

A:肯定有Al3+、SO42-,可能有K+、NH4+

B:肯定无Fe2+、Mg2+、CO32-,可能有Al3+

C:原溶液一定是明矾和MgSO4的混合溶液

D:不能确定的离子只能通过焰色反应来确定

上一题 下一题 0.0难度 选择题 更新时间:2010-07-09 06:06:54

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D

同类题3

Choose the best answer and complete the passage(选择最恰当的选项完成短文)(12分)

    The following are the posts in an Internet chat room. In this chat room, parents talk about some of the problems they have with their children.

    It is ever OK to lie to a child?My 10-year-old son plays soccer.He's not very good,but he loves it.Yesterday he played very 1.When he finished the game,he asked,"Did I play well?"I said,"Yes!You are a great scoor player!"Did I do the right thing?

    Yes,you did the right thing.White lies are a(n)2part of life.Sometimes you have to tell lies that do no harm.Your purpose was to make him feel good.Now he's ready to play soccer again.

    I don't think there is ever a good reason to lie to our children.Children learn honesty from the3they see.As parents, we should be honest in order to teach honesty to our children.Every lie requires five more lies.If you keep hiding truth from them, they will not   4 you.They will not respect you.Honesty is the first step to a good parent-child relationship.

    You lied to make your son feel better, but you 5 a good chance to teach him a life lesson.People should work hard for what they want.Maybe next time you can say, "No,you didn't play well today.Great soccer players practise a lot. Let's go and practise."The truth will make him6and a good soccer player.

    Parents should be honest to their childern,but they don't have to tell the whole truth. Next time when your son asks, "Did I play well?"You can say,"What do you think?" Then your son can tell you what he thinks.That way,everything you say is true, and you avoid truth that hurts.