课堂上同学们利用甲图装置做过氧化氢分解实验时，带火星的木条很_爱下问搜题

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问题问答题

课堂上同学们利用甲图装置做过氧化氢分解实验时，带火星的木条很难复燃，于是老师加了一个U形管，如乙图，带火星的木条较易复燃．请完成下列问题：

（1）写出实验室制取氧气的化学方程式：______．

（2）改用乙装置后能使带火星的木条复燃的原因：______．

答案

由于过氧化氢溶液中含有很多的水，制取的氧气中也会含有大量的水蒸气，导致甲中除了生成O₂外还有较多的水蒸气，而乙装置加了一个U形管，起到降温作用，降低了水蒸气的含量．由于含氧气浓度大带火星的木条才容易复燃，含氧气浓度小带火星的木条很难复燃．

故答案为：（1）2H₂O₂

二氧化锰

.

2H₂O+O₂↑；

（2）降低了水蒸气的含量，提高了氧气的浓度．

完形填空

My father was in the navy, which meant that my mother was married to both my father and the sea. As was often the       , we had to pack our belongings into boxes and    those we had grown to love. We would arrive at our new home and find ourselves once again standing at the pier (码头)      good-bye to my father as his ship pulled him away from us. My mother would turn my brother and me around before the ship was out of     , wipe our tears, and take us back home to start the process of    in the new environment again.
Throughout the years of changing     , schools and friends, there remained one constant in my childhood — my mother. For both my    and me, she was the cook, maid and teacher. She played these roles while    some type of part-time job. Leaving a       career is just one of the sacrifices which my mother made for my family as we moved around the world with our father every three years or so.    she had to deal with only a small budget, my mother,     , managed to make each house the very home that is safe and     .
This probably sounds like a depressing way to live,      with two small children: “single”
parenthood, short-term friendships, and the inability to    her career or establish a home. But it was not for my mother. She turned this    into adventure for us all! Each relocation (变换位置) was a chance to    another part of the world. My mother greeted each new culture, climate and neighborhood. Each new house was a    to rearrange furniture, make curtains and    pictures. Every part-time job was an opportunity to learn something new and work with interesting people.
No matter how difficult the life was, she was always having a    attitude. She always had strength in the face of struggle and change. My mother was so    all those years during my childhood — she was my island in a sea of change. She is my hero.

B．leave behind

B．comfortable

D．opportunity

A．experienced

单项选择题

DNA指纹鉴别技术出现于（）的英国。

A、1981年

B、1982年

C、1983年

D、1984年