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Biology/diffusion question and answer

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Expert: - 9/29/2010


Question
I read your answer for the question of phenolphthalein and sodium hydroxide may I also ask if I am correct.  The sodium hydroxide does diffuse across the dialysis tubing but the phenolphthalein does not---or do both  diffuse?

Answer
Dear Dee,

The phenolpthalein is a large molecule, and does not diffuse across the membrane.  This is why it is a good indicator the the dissociated ions of the NaOH *do* diffuse across the membrane, as the pH changes and you see the color change.

Hope that helps.

Dana

Biology

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Dana Krempels, Ph.D.

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I can answer biology-related questions in the areas of evolution, zoology, botany, genetics, and ecology. But I don't answer homework questions or provide ideas for your science fair projects. So students please do your learning the right way by reading your text assignments and studying!

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At the University of Miami, I teach Evolution and Biodiversity, Botany, Zoology, Genetics, Ecology, and a variety of seminars (e.g., the Biology and Evolution of Human Gender Roles).

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I have a B.S. in Biology and an A.B. in English from the University of Southern California (1980). I earned my Ph.D. in Biology in the area of evolutionary biology/visual physiology from the University of Miami in 1989.

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I am currently an "expert" in both the "Rabbits" and "Wild Animals" categories.

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