测定维生素C注射液的含量时，在操作过程中要加入丙酮，这是为了A_爱下问搜题

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问题单项选择题

测定维生素C注射液的含量时，在操作过程中要加入丙酮，这是为了

A．保持维生素C的稳定
B．增加维生素C的溶解度
C．使反应完全
D．加快反应速度
E．消除注射液中抗氧剂的干扰

答案

参考答案：E

解析：维生素C注射液中加入了亚硫酸盐为抗氧剂，用碘量法测定含量时有干扰，预先人丙酮可使亚硫酸盐与丙酮发生加成反应，消除干扰。

完形填空

Once there was a very brilliant, creative and learned man. He gained much ____36_____while traveling throughout the world. Unfortunately he lost his legs and left arm in a traffic accident, leaving only a finger and thumb on his right hand. He became so ____37_____ that he was afraid he would spend his life _____38_____ and would no longer be able to use his life in a(n) ____39_____way.
One day, he remembered how he had always loved getting ____40_____. He realized that he still had partial ____41_____ of his right hand and could write with ____42_____. Then, he had an idea. “Why not write to other people who need encouragement?”
He ___43___ where he could find those who could be encouraged if they read his letters. He thought of people in ____44___. Many of them had hope of regaining their ____45___ . Others would keep feeling depressed and remain put away for the rest of their lives. He decided that he must try to __46____ them. So he wrote to a prison ministry about sending letters to the prisoners. The prison minister replied that writing to the prisoners would be ____47____. However, it would be against prison rules for the prisoners to write back.
____48_____with the intention, the man began sending 49 messages of God’s love, hope, strength, and encouragement. He wrote twice a week, testing his strength and ability to the ___50____. He poured his heart and soul into his words, ___51_____ his experience, sense of humor, optimism, and faith.
It was difficult to write those letters, especially without hope of any ___52___. Frequently, he felt discouraged, wondering if anyone ___53____read his letters. However, this was his ___54____chance，so he determined to continue.
At last, he received a letter from the prison officer, which said, “Please write on the best paper you can afford. Your letters are passed from cell (牢房) to cell until they almost fall to ____55___!”
We all have unique experiences, abilities and talents. We can discover ways to reach others in need of encouragement and strength.

B．embarrassed

C．comfortable

问答题

便血常见的原因