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Щавель, картофель и гортензии хорошо растут в кислотной почве, pH которой равен 4. Чему равна молярная концентрация ионов водорода и гидроксида в этой почве?
Ответы 2
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^ означает возведение в степень
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Автор:
cowboy2m3o - 5 лет назад
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pH=-lg[H(+)]концентрация H(+)=10^(-4) моль/литрконцентрация OH(-)=10^-14/10^-4=10^-10 моль/литр
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Автор:
emiliocoleman338 - 5 лет назад
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Every evening she came down through the darkness of the alley, emerging in the bright light of the street like the sudden appearance of a frightened child far from home. I knew that she had never reached the end of the alley before eight o'clock, and yet there were evenings when I ran there two hours early and waited beside the large green and red hydrant until she came. During all those months I had known her she had been late only two or three times, and then it was only ten or fifteen minutes past eight when she came.
Rachel had never told me where she lived, and she would never let me walk home with her. Where the alley began at the hydrant, was the door through which she came at eight and the door which closed behind her at ten. When I had begged her to let me walk with her, she always pleaded with me, saying that her father did not allow her to be with boys and that if he should see us together he would either beat her unmercifully or make her leave home. For that reason I kept the promise I had given, and I never went any farther than the entrance to the alley with her.
"I'll always come down to see you in the evening, Frank," she said and added hastily, "as long as you wish me to come. But you must remember your promise never to try to find where I live, or to walk home with me."
I promised again and again.
"Perhaps some day you can come to see me," she whispered, touching my arm, "but not now. You must never go beyond the hydrant until I tell you that you may."
Rachel had told me that almost every time I saw her, as if she wished to impress upon me the realization of some sort of danger that lay in the darkness of the al¬ley. I knew there was no physical danger, because around the corner was our house and I was as familiar with the neighbourhood as anyone else. And besides, during the day I usually walked through the alley to our back gate on my way home, because it was a short cut when I was late for supper.
I knew Rachel and her family were poor, because she had been wearing the same dress for nearly a year. It was a worn and fragile thing of faded blue cotton. I had never seen it soiled and I knew she washed it every day. It had been mended time after time; carefully and neatly. I wished to offer to buy her a dress with the few dollars I had saved in my bank, but I was afraid to even suggest such a thing to her. I knew she would not have allowed me to give her the money, and I did not know what we would do when the dress became completely worn out. I was certain that it would mean the end of my seeing her.-
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