问题 实验题

有一学生在实验室测某溶液的pH,实验时,他先用蒸馏水润湿pH试纸,然后用洁净干燥的玻璃棒蘸取试样进行检测。

(1)该学生的操作__________(填“正确”或“错误”),其理由是__________________;

(2)如不正确请说明理由,同时请分析是否一定有误差?__________________;

(3)若用此方法分别测定c(OH-)相等的氢氧化钠溶液和氨水的pH,误差较大的是__________,原因是__________________;

(4)只从下列试剂中选择实验所需的试剂,你能否区分0.1 mol·L-1 硫酸溶液和0.01 mol·L-1 硫酸溶液?__________,简述操作过程。__________________。

试剂:

A.紫色石蕊试液  B.酚酞试液  C.甲基橙溶液  D.蒸馏水  E.氯化钡溶液  F.pH试纸

答案

(1)错误;该学生测得的pH是稀释后溶液的pH

(2)该学生操作错误,但不一定产生误差。因为原溶液不是中性的,稀释后溶液pH发生了变化,只是弱酸或弱碱溶液变化程度小些,若中性溶液,稀释不会产生误差

(3)氢氧化钠溶液;稀释过程中NH3·H2O继续电离OH-,减弱了因稀释OH-浓度减小程度,所以测得氢氧化钠溶液误差较大

(4)能;用玻璃棒分别蘸取两种溶液滴在两张pH试纸上,用标准比色卡比较其pH,pH较大的是

0.01 mol·L-1硫酸溶液

阅读理解

阅读理解

       Are your parents helicopters? That's a new term I read about. It describes parents who hover(原意指发飞机盘旋)  over their children. They worry about every little thing in their children's life: Are you

hungry? Are you thirsty? Do you feel cold? Do you need more books? .

       These parents love their children and want to make sure that everything in their life is perfect. Some

kids may find that annoying but others like being pampered. The pampered kids like the idea of being

waited on hand and foot. They like the idea of not having to make decisions.

       I don't think this is a good idea. I think it's important for kids to do things and make decisions by

themselves. This helps them grow up and become  responsible (负责任的 )  persons.

       How can you become responsible? It's easy: just start with little things. You can make your own

meals sometimes or help with cooking. You can also make your own bed and clean your room...

       Your parents are helicopters because they love you. So, tell them that you know it and that they

really shouldn't worry. Tell them they can land the helicopters because you are a responsible kid.

1. The parents become helicopters because _______ .        

A. they love their children too much, and hope their children's lives are perfect

B. they don't want their children to do anything except study

C. they have much free time to look after their children

D. they want to do everything for their children

2. If Mary's mother is a helicopter, what should Mary do according to the passage?        

A. Do everything without her mother's permission.

B. Argue with her mother and then say sorry to her mother.

C. Thank her mother for all that her mother has done for her.

D. Tell her mother that she understands and that her mother shouldn't worry.

3. The meaning of the underlined word is " _________" in Chinese.  

A. 关怀  

B. 歧视  

C. 娇惯  

D. 鼓励

4. How can children become responsible?         

A. Do as parents say.

B. Start with little things.

C. Let parents do everything.

D. Let others help them make decisions.

5. Which of the following is the best title?        

A. How to be perfect helicopters

B. Let your helicopters rest

C. Thanks for helicopters

D. The term of helicopters

填空题