在一密闭容器中，有甲、乙、丙、丁四种物质，在一定的条件下，充_爱下问搜题

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问题选择题

在一密闭容器中，有甲、乙、丙、丁四种物质，在一定的条件下，充分反应，测得反应前后各物质质量如下表

物质	甲	乙	丙	丁
反应前质量(g)	4	18	10	1
反应后质量(g)	待测	2	21	10

关于此反应，下列认识正确的是( )

A．该变化的基本反应类型一定是置换反应 B．参加反应的甲、丙的质量比为2:11

C．丙、丁的相对分子质量比一定为11: 9 D．甲反应后的质量为0g

答案

答案：D

题目分析：根据质量守恒定律可知，反应前物质质量总和=反应后物质质量中，即 4+18+10+1=待测+2+21+10，则甲的待测值=0；由此可知，质量减少的物质是甲、乙，即二者均为反应物；质量增加的物质是丙、丁，即二者均为生成物，故该反应可表示为：甲+乙→丙+丁。

A、由于无法判断反应物和生成物的种类，故无法判断该变化的基本反应类型，错误；

B、参加反应的甲、丙的质量比=4：11，错误；

C、由于无法确定化学反应中的各计量数，故无法判断丙、丁的相对分子质量比，错误；

D、根据上面的分析，甲反应后的质量为0g，正确。故选D

点评：首先根据反应前后物质的质量关系判断反应的反应物与生成物，反应后质量增大的物质为反应的生成物、质量减小的物质为反应的反应物；解答本题还要根据质量守恒定律来判断，即参加反应的物质的质量之和等于反应后生成的物质的质量之和。

单项选择题

女性，33岁。双侧 * * 胀痛3年，并触及不规则 * * 肿块，伴有触痛，月经前出现 * * 胀痛，经后自行消退，应考虑为（）。

A. * * 纤维腺瘤

B.乳腺癌

C.乳腺肉瘤

D.乳腺囊性增生病

E.乳管内 * * 状瘤

完形填空

Half a year before graduation from college, my son began to seek a job.    the financial crisis, fewer companies would like to      new staff. My son targeted a company that was    to employ only one person      there were more than 20 people filing their resumes﹙简历﹚.
After the interview, there would only be 3 who could enter the final round, which would later     one person to be employed. Everything seemed to go quite       and my son passed the first round and entered the final round in a week.
On the day of the final interview, my son and the      two candidates（候选人）arrived at the interview place on time,       the test. The interview was unbelievably     . The interviewer only said to them, “All of you are very super. Please go home and wait for our      . We will tell you the      in 3 days. Good luck to all of you” On the morning of the third day, my son received a text from the company shortly after breakfast that he was not employed. We all felt very      .
In nightfall that day, my son suddenly told me       on phone, “Dad, I have been employed!” Greatly surprised, I could not wait to ask him, “What’s the whole      ?” My son told me that he received another text saying that he was employed. Actually the first text sent to my son was also       of the test in the interview. Three men received the same text this morning and only my son’s       was “Thank you” while the others said “Goodbye”.
Only then did I know that my son’s hope       in that way. That is, when you feel disappointed, do not       to say “Thank you” to the one who disappoints you. Saying “Thank you” shows respect for others’ work and shows your great      . Therefore, while under the same condition, you will get the upper hand in terms of       compared with others!

A．watching over

B．waiting for

C．thinking about

D．looking into

A．advertisement

D．disappointed

B．unselfishness

B．opportunities

D．shortcomings