问题 问答题 简答题

简述用皿铬酸钾法侧水中COD的步骤。

答案

参考答案:

①取25mL水样于烧瓶中,加人15mL重铬酸钾溶液,在不断摇动的情况下,慢慢加入40mI.浓硫酸.使混合后硫酸浓度约50%,加人0.5g硫酸银;②加人数粒玻璃珠,在回流情况下加热煮沸2h;③稍冷却,用25mL蒸馏水洗冷凝管,将烧瓶中溶液称人250mL锥形烧瓶中,使溶液的总体积约为150mL;④冷却后加2一3滴试亚铁灵指示剂,用硫酸亚铁铵标准溶液滴定至溶液由黄色经绿蓝色变为红蓝色,记录消耗硫酸亚铁钱毫升数;⑤以蒸馏水代替水样,按同样操作做空白试验。

阅读理解

Summer school is something a kid will never forget. For some, it’s a way to advance past their classmates. For most, summer school is a requirement in order to graduate with their classmates. I can remember being forced into taking a summer school course. It was not the school that forced me into this awkward situation; it was my mother.

I was a 16-year-old kid in a new school. My school did not offer summer courses so I had to take my course at an alternative school in the city. It was an experience I will never forget. I was not concerned with making friends. I was there to get credit (学分) for a course that I should have received credit for the previous semester. It was my doing that landed me in the situation and it was important that I understood this.

The fees were lowest but the experience was amazing. I enjoyed. I didn’t miss the day. The course was from Monday to Friday for an entire month. I passed the course with an A. I was thrown into an awkward situation and actually enjoyed it. My friends didn’t even know I took the course. Most of them were still sleeping by the time my course ended each day.

Awkward situations are so important for personal growth. This situation made me feel more independent. I made friends. I finally understood what sacrifice and hard work were all about. While attending college, I remembered how much I enjoyed summer school and I chose to take summer school in my first three years of college. Some kids get pushed too much but some don’t get pushed enough. I was never pushed enough.

Enable your children to struggle for success. If your child needs summer school you explain to them why it’s important. Some parents are surprised by the situation and may want to be more involved in their children’s education. Follow through and follow up.

小题1:Most students go to the summer school in order to ______.

A.find good jobs after graduation

B.become top students in their class

C.have a chance to make more friends

D.graduate successfully on time小题2:What made the author go to summer school for the first time?

A.What he had done .

B.His mother’s wish.

C.His own requirement.

D.Study competition.小题3:Which of the following was NOT the benefit got by the author through attending summer school?

A.It helped him get rid of bad habits.

B.It helped him make new friends.

C.It helped him understand what sacrifice and hard work were.

D.It increased his independence.小题4:From the last paragraph we can learn that the author ______.

A.does not like summer school at all even though it is useful

B.thinks summer school is unnecessary for children

C.encourages parents to make their children attend summer school

D.is against forcing children to attend summer school小题5:What does the author think of summer school?

A.He thinks it is awkward.

B.He thinks it is significant.

C.He doesn’t think it is suitable.

D.He thinks nothing of it.

单项选择题 A1/A2型题