问题 填空题

已知H+(aq)+OH-(aq)H2O(l) ΔH="-57.3" kJ·mol-1,回答下列问题。

(1)用含20 g NaOH的稀溶液跟足量稀盐酸反应放出    kJ的热量。 

(2)用含2 mol H2SO4的稀溶液跟足量稀NaOH反应,此反应的中和热为      。 

(3)如果将(1)反应中的稀盐酸换成稀醋酸,反应放出的热量       (填“大于”“小于”或“等于”)原来(1)放出的热量。 

答案

(1)28.65 (2)57.3 kJ·mol-1 (3)小于

(1)="0.5" mol,所以0.5 mol NaOH与足量稀盐酸反应放出的热量为0.5 mol×57.3 kJ·mol-1="28.65" kJ。

(2)据中和热的定义可知,中和热与强酸、强碱的物质的量的多少无关,中和热为57.3 kJ·mol-1

(3)因醋酸为弱酸,用NaOH中和时,需不断地电离出H+,而电离过程要吸收热量,故反应放出的热量会减小。

选择题
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完形填空

     Louise was 72 years old and she lived by herself. The first thing she noticed when she came

downstairs that Sunday morning was that her    1   window was open. In fact, it was so wide open that

she had    2   closing it. Then she realized that things were not in their proper    3   . Finally, when she

found her empty    4  on the kitchen table, she realized the awful    5   . At first, she didn't know what to

do. Then she decided to   6   her son, Derek.

     Derek's wife Sybil answered the phone, "It's your mother," she    7   him, coldly. Louise told Derek

about the open window, about things being in the wrong places and about the    8   missing from her

purse.

     "All right," said Derek, "Don't    9   anything. I'll be    10   in half an hour."

     Louise    11   and made herself a pot of tea and some toast. Then she went from room to room

wondering    12  anything else was missing.

     When Derek arrived, he was content to   13   her looking so calm. "Have you rung the     14  ?" he

asked. "No? Then I'll do that straight away." So he rang the police.

     As it was Sunday,   15  the only detectives were out. However, the police were polite, but vague

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     Derek telephoned his wife. "I'm not sure when I'll be home, love," he told her. "I've got to    17  for

the police." While Derek and his mother waited, Derek    18  the catches(挂钩)on the windows and

locks on the doors. All of them were old and some of the catches hardly    19   at all. Derek felt    20   .

His mother was an old woman, after all. "I'll have to change all these," he told her.