问题 问答题 简答题

试述溴酸钾法测定异烟肼的原理与滴定度。

答案

参考答案:

异烟肼具有较强的还原性,在酸性溶液中可以用溴酸钾滴定。异烟肼与溴酸钾反应的化学计量摩尔比为3:2,用甲基橙指示液指示终点,终点时,微过量的溴酸钾氧化甲基橙使其在酸性溶液中的粉红色消失,以指示终点的到达。每1mL溴酸钾滴定液(0.01667mol/L)相当于3.429mg的异烟肼。

阅读理解

阅读理解。判断下列句子是否与短文内容相符,相符的填"T",不相符的填"F"。

     You may know the song Happy Birthday very well. But do you know who wrote this song and for

 whom it was written?

     Let me tell you a story.

     About one hundred years ago, there was a girl in the USA. She loved children very much and wrote

 many songs for children. One of them was the song Good Morning To You. The song was very popular

 at that time among children, but not all grown-ups ( 成年人 ) knew it.

     The girl was very poor. Once her friends invited her to a little child's birthday party. She felt happy but

 sad because she had no money to buy a present for him. Finally she decided to sing the song Happy Birthday in the melody( 曲调 ) of Good Morning to You for the little boy.

     When her friends heard the song at the party, they were very happy. "How wonderfully she is singing!

  We have not heard this song before. It's a special present," said someone. And they learned to sing it

 together.

     Later, the song became very popular throughout the world. People like it because it's simple and

  friendly.

    

( ) 1. Happy Birthday is a old song. Nobody knows who wrote the song Happy Birthday.

(     ) 2.The song Happy Birthday is a song from America.

(     ) 3. The melody of Happy Birthday comes from the melody of Good Morning to You.

(     ) 4. The girl first sang the song for a little child as a birthday present.

(     ) 5. The girl knew the song would be popular before she came to the party.

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