问题 问答题

初中化学实验室有一瓶失去标签的盐溶液,实验测得其呈碱性,其PH一定       ,该盐的化学式可能是        .检验碳酸盐的试剂是       ,检验时产生的实验现象为                                          

答案

大于7;Na2CO3;稀盐酸和石灰水;有气体产生且产生的气体能够使澄清的石灰水变浑浊.

题目分析:因为实验测得盐溶液呈碱性,所以其PH一定大于7;常见的碳酸钠是显碱性的盐,检验的方法是:取适量溶液滴加稀盐酸,能够产生气泡,再把产生的气体通入澄清的石灰水中,若石灰水变浑浊,则说明含有碳酸根离子

点评:本题考查了溶液的酸碱性与pH的关系及碳酸根离子的检验,依据碳酸根离子的特性分析即可.

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A Narrow Escape

Shortly after the war, my brother and I were invited to spend a few days’ holiday with an uncle who had just returned from abroad. He had rented (租) a cottage in the country, although he hardly spent much time there. We understood the reason for this after our arrival: the cottage had no comfortable furniture in it. Many of the windows were broken and the roof leaked (漏水), Cwet.

On our first evening, we sat around the fire after supper listening to the stories our uncle told of his many adventures in distant countries. I was so tired after the long train journey that I would have preferred to go to bed; but I could not bear to miss any of my uncle’s exciting stories, He was just in the middle of describing a rather terrifying experience he had once had when there was a loud crash(倒塌声) from the bedroom above, the one where my brother and I were going to sleep.

When we got to the top of the stairs and opened the bedroom door, a strange sight met our eyes. A large part of the ceiling had fallen right on to the pillow(枕头)of my bed.

66. The uncle disliked the rented cottage for the reason that _____.

A. there were no beds in it

B. the windows were broken and the roof leaked

C. it was too old for him to live in

D. it was very rainy in the area

67. On the first evening, the writer was very sleepy, _____.

A. but he did his best not to miss any stories

B. so he had to go to bed early

C. because he was tired of his uncle’s stories

D. and he was gradually falling asleep while listening

68. A narrow escape means ___.

A. A person runs away from a danger through a narrow door.

B. A person escapes a danger by luck.

C. A person escapes a danger easily.

D. A person runs away from a danger easily.

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