问题 阅读理解

阅读理解

     Do you hope to do a lot of homework every evening? Are you interested in your classes? Who do you want to teach

you? Maybe you have lots of questions in your mind before school starts.

     Well, I want to give you some good advice on these problems.

     First, keep calm(冷静的). Don't worry about all the questions you have. Put your heart into learning,and you can find

something you are interested in. Do it actively.

     Second, try your best to finish your homework quickly. Don't spend a lot of time on it. Do more reading or writing in

English. Think about the problems you have and solve them at once. Don't stay up late, or you can't study well the next

day.

     Third, think of something instead of copying(抄写) or repeating(重复). If you can remember the words in your way,

you can tell your teachers you don't like the way of copying them again and again. Be sure you can pass the test. I think

your teachers will agree with you. And they can give you something interesting to do.

     School is really a good place for you to learn. Believe in your teachers and yourself. You are the best one and you can

do everything well.

1. The writer writes the passage to __________

A. give students some good ways of learning.

B. ask students not to listen to their teachers.

C. ask students not to do their homework.

D. tell students what a good teacher is.

2. How many pieces of advice does the writer give us?

A. 3

B. 4

C. 5

D. 6

3. What does the writer tell students to do about their homework?

A. They should spend a lot of time on it.

B. They should stay up late doing it.

C. They should do more reading or writing in English.

D. They should have boring work to do.

4. What's the third piece of advice about?

A. How to get on with friends?

B. How to get high grades.

C. What kind of schoolwork is better for students.

D. How to finish the homework in a short time.

5. According to the passage,students should believe in __________.

A. themselves and their teachers

B. themselves and their parents

C. their parents and teachers

D. themselves and their classmates

答案

1-5 AACCA

选择题
实验题

(12分)实验室常利用甲醛法测定某(NH4)2SO4样品中氮的质量分数,其反应原理为:4NH4++6HCHO = 4H+ +(CH2)6N4+6H2O,然后用NaOH标准溶液滴定反应生成的酸。某兴趣小组用甲醛法进行了如下实验:

步骤①用电子天平准确称取样品1.5000 g。

步骤②将样品溶解并冷却后,完全转移到250 mL容量瓶中,定容,充分摇匀。

步骤③移取25.00 mL样品溶液于250 mL锥形瓶中,加入10 mL 20%的中性甲醛,摇匀、静置5min,加入2滴酚酞试液,用NaOH标准溶液滴定到终点。重复步骤③操作2次。

(1)根据步骤③填空:

①碱式滴定管用蒸馏水洗涤后,直接加入NaOH标准溶液进行滴定,则测得样品中氮的质量分数将       (填“偏高”、“偏低”或“无影响”)。

②锥形瓶用蒸馏水洗涤后,水未倒尽,则滴定时用去NaOH标准溶液的体积将      

(填“偏大”、“偏小”或“无影响”)。

③滴定时边滴边摇动锥形瓶,眼睛应观察       

A.滴定管内液面的变化

B.锥形瓶内溶液颜色的变化

④滴定达到终点时,酚酞指示剂由    色变为     色,半分钟内不退色。

⑤滴定后俯视读数,测得样品中氮的质量分数将     (填“偏高”、“偏低”或“无影响”)。

(2)滴定结果如下表所示:

滴定次数待测溶液的体积/mL标准溶液的体积
滴定前刻度/mL滴定后刻度/mL
125.001.0221.04
225.002.0022.00
325.000.2020.21
    若NaOH标准溶液的浓度为0.1000 mol·L-1,则该样品中氮的质量分数为         。(保留两位小数)