问题 问答题

若成人每天食用7.5g加碘食盐,就能同时摄人(成人每天需要的)150×10-6g碘.问每千克加碘食盐中含______g碘.若加入的是碘化钾或碘酸钾(相对分子质量分别为166和214),则每千克食盐中应加______g碘化钾或______g碘酸钾(KIO3).加碘化钾的食盐若保存不当,半年中碘损失约90%,损失碘的原因是______.(提示:单质碘会升华)

答案

7.5g加碘食盐的质量为:7.5g×1×10-3kg/g=7.5×10-3kg

每千克加碘食盐中含碘的质量为:

150×10-6g
7.5×10-3kg
=2.0×10-2g

每千克食盐中应加碘化钾的质量为:0.02g÷

127
166
×100%=2.61×10-2g

每千克食盐中应加碘酸钾(KIO3)的质量为:0.02g÷

127
214
×100%=3.37×10-2g

加碘化钾的食盐若保存不当,容易被空气中的氧气氧化成碘单质;

故答案为:2.0×10-3;  2.61×10-2;  3.37×10-2;  被空气中的氧气氧化成碘单质.

阅读理解

阅读理解。

      A man made a nice talk machine(机器). It could weigh people’s weight . The man wanted to try the

machine before he could make a lot of them. He put the machine into the waiting of a station. There were

a lot of people in and out.

The first one who used the machine was an Indian woman. She stood on the machine. The machine thought for a few seconds(秒) to decide which language to speak.

     "Good morning, madam,: it said in Indian, " Your weight is 72 kilos. That’s three kilos more. If you eat more fruit and vegetables, you’ll be soon all right . Please have a nice day."

The second one to use the machine was a Chinese girl. She stood on the machine and waited to hear her

weight.

     "Good morning, Miss,” The machine said in Chinese .Your weight is 45 kilos .It’s all right for your age and height. Go on to eat what you eat every day. Please have a nice day."

The third one to use the machine was a very fat American woman .She thought for a long time to stand on

the machine. The machine spoke highly in English, “ Good morning, Will one of you get off?”

1.What made the machine so special?

A. It could talk just like a man.

B. It could weigh people's weight.

C. It could know everyone.

D. A and B

2.What did the machine tell the Indian woman?

A. She was a little lighter

B. She was a little heavier

C. It couldn't speak Indian

D. To eat what she wanted to eat

3.How was the American woman?

A. She was healthy

B. She liked thinking

C. She was too heavy

D. The machine liked her

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