问题 选择题

下列试剂保存方法错误的是  [ ]

A.金属钠:煤油中

B.氢氧化钠:磨口瓶塞的广口瓶中

C.白磷:水中

D.浓硝酸:棕色的细口瓶中

答案

答案:B

题目分析:
选项A金属钠化学性质相当活泼,需要隔绝空气密封保存,由于煤油的密度小于钠,且不与钠发生反应,所以金属钠保存在煤油中,故A正确;
选项B烧碱能与玻璃中的二氧化硅反应生成具有粘合性的硅酸钠,容易将瓶口和瓶塞粘结在一起,故B错误;
选项C白磷不溶于水,与水不反应,可保存在水中,故C正确;
选项D硝酸见光易分解,应保存在棕色试剂瓶中,故D正确。
故选:B.
改错题

短文改错

假定英语课上老师要求同桌之间交换修改作文,请你修改你同桌写的以下作文,文中共有l0 处语言错误,每句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。

增加:在缺词处加一个漏字符号(∧) ,并在其下面写出该加的词。

删除:把多余的词用斜线( \) 划掉。

修改:在错的词下划一横线,并在该词下面写出修改后的词。

注意:1. 每处错误及其修改均仅限一词;

            2 .只允许修改l0 处,多者( 从第11 处起) 不计分。

Dear Fangfang,

     I’m sorry to learn that you were not getting on well with your English study recently. I’d

like to give you some advice on learning English.

     First of all, you should be confidently in yourself, which is ? first step in learning English well.

Secondly, you’d better make friends with the students who are good at English, so  they  are

very likely to helping you when you meet difficulties.Thirdly, learning English well is a long 

process.Remember: to reward yourself when you have made progress, that will inspire you

 greatly.Anyway, you must work hard on English and never give up learning it.Just believe

in yourselves.Where there is a will, there is a way.

     Hope my suggestions will give you some of help.

                                                                                                                   Sincerely yours,

                                                                                                                                 Li Ming

单项选择题 A1/A2型题