Xtra Problem Titration of Glycine (answers)

# Xtra Problem Titration of Glycine (answers) - @pH 10.2 NH 2...

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The amino acid glycine is often used as the main ingredient of a buffer in biochemical experiments. The amino group of glycine (pK a =9.6) can exist either in the protonated form (-NH 3 + ) or as a free base (-NH 2 ) because of the reversible equilibrium: R- NH 3 + ↔ R -NH 2 + H + a) In what pH range can glycine be used as an effective buffer due to its amino group? 8.6 10.6 b) In a 0.1 M solution of glycine at pH 10.2, what fraction of glycine has its amino group in the -NH 3 + form? pH = pk a + log °±? ²³? + 0.6 = log °±? ²³? + 4 = °±? ²³? + NH 3 + = 1/5 c) How much 5M HCL must be added to 1.0L of 0.1M glycine at pH 10.2 to bring its pH to 8.6?

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Unformatted text preview: @pH 10.2 NH 2 = 0.8 eqvivalents → to get to pH 8.6,which is pk a – 1 and therefore 10% titrated (0.1 equivalent), we have to add 0.7 equivalents of HCL 1 equiv. = 0.1mol (0.1Mx1.0L) → 0.7 equiv. = 0.07mol → 5M = ? . ?´ ?µ¶ · →x = 14ml d) When 99% of the glycine is in its -NH 3 + form, what is the numerical relation between the pH of the solution and the pK a of the amino group? pH = pk a + log ¸ ¹¹ ~ pH = pk a + log ¸ ¸?? → pH = pk a – 2 result: at 1% titrated → pH = pk a – 2 at 99% titrated → pH = pk a + 2...
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Xtra Problem Titration of Glycine (answers) - @pH 10.2 NH 2...

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