问题 实验题

已知锌与稀硫酸反应为放热反应,某学生为了探究其反应过程中的速率变化,用排水集气法收集反应放出的氢气,实验记录如下:

时间(min)12345
氢气体积(mL)30120280350370
 

反应速率最大的(填0~1、1~2、2~3、3~4、4~5min)时间段为        。原因是                                                           

②反应速率最小的时间段为             ,原因是                                 

(2)另一学生也做同样的实验,由于反应太快,测量氢气的体积时不好控制,他就事先在硫酸溶液中分别加入等体积的下列溶液以减慢反应速率。

A.蒸馏水      B.CuCl2溶液      C.NaCl溶液

你认为他的做法可行的是                               (填相应字母);做法不可行的是             (填相应字母),做法不可行的理由是                     

答案

(1)①2~3min 该反应是放热反应,此时温度高,H+浓度大

②4~5min 此时H+浓度小

(2)A、C; B; Zn 置换出Cu,形成Cu—Zn原电池,使反应更快

题目分析:温度越高,反应速率越快;离子浓度越小,反应速率越慢;增大固体接触面积,反应速率加快,硫酸溶液中加入等体积的NaCl溶液,相当于加水将硫酸稀释,所以氢离子浓度减小,据此可以解答。

(1)①根据表中数据可知,0~1、l~2、2~3、3~4、4~5min各时间段生成氢气的体积分别为30、90、160、70、20,可以看出反应速率最大的是2~3min。这是由于锌与稀硫酸反应为放热反应,随反应的进行,温度越来越高,反应速率加快。

②反应速率最小的时间段为4~5min,这是由于随着反应的进行,氢离子浓度越来越小,反应速率越来越慢。

(2)选项A中在硫酸溶液中加入等体积的蒸馏水,相当于加水将硫酸稀释,所以氢离子浓度减小,反应速率减慢,故A正确;选项B中加入氯化铜溶液,锌置换出铜,形成Cu—Zn原电池,使反应速率更快,B不正确;选项C主事先在硫酸溶液中加入等体积的NaCl溶液,相当于加水将硫酸稀释,所以氢离子浓度减小,反应速率减慢,故C正确。

点评:该题是中等难度的试题,也是高考中的常见题型,有利于培养学生规范严谨的实验设计能力,有助于提升学生的学科素养,提高学生的应试能力。该类试题主要是以实验基本操作为中心,通过是什么、为什么和怎样做重点考查实验基本操作的规范性和准确性及灵活运用知识解决实际问题的能力。

完形填空
I went back to China as soon as school was over at the end of June. And I returned to Canada on August 17th.
It’s      to go back to China this summer, because of the A(H1N1)flu. Everybody seemed to be       . The easiest thing for us to do was to wear masks(口罩)on the plane, as my mom suggested. However, it was not      to wear a mask for ten hours. I decided to put the masks into my bag        wearing them.
Everything seemed OK     the flight. I saw only five people wear masks all the time. When we arrived in Beijing, some      came into the plane and took our temperature. Fortunately,       had a fever. Therefore, I was able to get home on time.
However, everything went wrong after I got home. I became sick, with a sore throat and a fever because I had not     my mom’s words. Luckily, I just had a common       . while I was sick in bed, I thought that if I had listened to my mom at first, I      would have never caught the cold.
It’s always wise to listen to your mom’s suggestions.
小题1:
A.difficultB.impossibleC.easyD.important
小题2:
A.happyB.nervousC.excitedD.sad
小题3:
A.necessaryB.healthyC.unfairD.comfortable
小题4:
A.thanks forB.instead of C.because ofD.except for
小题5:
A.beforeB.byC.afterD.during
小题6:
A.policemenB.doctors C.engineersD.reporters
小题7:
A.somebodyB.anybodyC.nobodyD.everybody
小题8:
A.followed B.heardC.knownD.understood
小题9:
A.stomachacheB.toothacheC.coldD.headache
小题10:
A.differentlyB.particularly C.usuallyD.probably
单项选择题