问题 计算题

(8分)现有25℃时pH=12的NaOH溶液100ml,欲用以下几种方法将其pH调为11,回答下列问题。(假设稀溶液混合后的总体积等于两溶液的体积之和)

(1)此pH=12的NaOH溶液中由水电离产生的c(H+)=              

(2)加水稀释,需加水的体积为              ml;

(3)加入pH=2的盐酸,需加盐酸的体积为              ml;

(4)加入pH=10的NaOH溶液,需加NaOH溶液的体积为          ml;

答案

(1)c(H+)=10-12 mol·L-1;  (2)900 ml;  (3)81.8ml;  (4)1000ml

题目分析:(1)氢氧化钠溶液中H+全是由水电离出来的,pH=12的NaOH溶液中c(H+)=10-12 mol·L-1。,所以水电离出来的c(H+)=10-12 mol·L-1

(2)设加水体积为VmL,,V=900。

(3)设加水体积为VmL,,V=81.8。

(4)设加水体积为VmL,,V=1000。

点评:酸碱混合计算pH时,若酸过量,应先计算c(H+),再求pH;若碱过量,应先求c(OH-),再求c(H+),最后求pH。

完形填空

阅读下面对话,按要求完成相关任务。

Stephen will finish school this summer. He plans to find a job in UNICEF. Now he is being interviewed by a UNICEF worker.

(S: Stephen                   W: worker in UNICEF)

W: So, Stephen, please say something about yourself.

S: Well, I love children so much. My mother works in a primary school, so I learn a lot about children and I think this might be useful.

W: I’m sure it is. Do you speak many languages? Ours is an international organization and it’s quite often that we meet children from different countries.

S: Yes. I’m good at French and English. I’m taking Chinese at evening classes. I learned Japanese at school, too.

W: Excellent. 告诉我你为什么想得到这份工作。

S: Well, it sounds interesting, worker, like, experience, I, as , some, would, a , to, charity, get . Maybe one day I’ll set up my own charity.

W: I see. What are your characteristics, may I ask?

S: I’m patient, generous and easy-going.

W: Good. What do you think you could offer us, Stephen?

S: I think my knowledge of languages and personalities would be useful. I enjoy working with children and you can always believe me. I’m also fit and healthy.

W: What do you think your disadvantages are?

S: I’m not outgoing. I’m very shy when I first meet people. I find it difficult to talk to them and make conversation, but when I know people quite well I’m much more self-confident.

W: Thank you very much. Stephen. We’ll call you next week.

小题1: Where does Stephen’s mother work?                                        ________

小题2:Which language is Stephen taking at evening classes.  English, Chinese or Japanese?  _______

小题3: 将文中划线部分的单词组成一个通顺的句子。        ______________________________

小题4: 将文中汉语“告诉我你为什么想得到这份工作。”译成英语。  ________________________

小题5:What are Stephen’s advantages in asking for this job?(列出四个方面)              ________

单项选择题