a) Lysine is an essential amino acid. It is taken by some people as a nutritional supplement in the form of a hydrated crystalline solid with the formula C6H14N2O2.xH₂0. To control the dose of lysine, it is essential to know the complete formula of the hydrate, which means determining the value of x. To determine the value of x in lysine hydrate, a pharmacist used a direct titration method. She dissolved 6.258g of the compound in approximately 100mL of distilled water and then made this up to 250mL in a volumetric flask. She then titrated 25mL aliquots of this solution with a standardized NaOH solution of concentration 0.1050 mol dm-3, obtaining a mean titre of 36.30 mL. In titrations, lysine behaves as a monoprotic acid. Use these data to determine the value of x in lysine hydrate. b) In a second experiment to verify the value of x, the pharmacist heated a 3.752g sample of the lysine hydrate to drive off all the water. When she reweighed the sample, the mass was 3.278 g. Use this data to obtain another value for x. c) What is the most likely reason why the value of x obtained in the second experiment does not exactly agree with the value form the first experiment?

a) Lysine is an essential amino acid. It is taken by some people as a nutritional supplement in the form of a hydrated crystalline solid with the formula C6H14N2O2.xH₂0. To control the dose of lysine, it is essential to know the complete formula of the hydrate, which means determining the value of x. To determine the value of x in lysine hydrate, a pharmacist used a direct titration method. She dissolved 6.258g of the compound in approximately 100mL of distilled water and then made this up to 250mL in a volumetric flask. She then titrated 25mL aliquots of this solution with a standardized NaOH solution of concentration 0.1050 mol dm-3, obtaining a mean titre of 36.30 mL. In titrations, lysine behaves as a monoprotic acid. Use these data to determine the value of x in lysine hydrate. b) In a second experiment to verify the value of x, the pharmacist heated a 3.752g sample of the lysine hydrate to drive off all the water. When she reweighed the sample, the mass was 3.278 g. Use this data to obtain another value for x. c) What is the most likely reason why the value of x obtained in the second experiment does not exactly agree with the value form the first experiment?

Chemistry for Engineering Students

4th Edition

ISBN:9781337398909

Author:Lawrence S. Brown, Tom Holme

Publisher:Lawrence S. Brown, Tom Holme

Chapter4: Stoichiometry

Section: Chapter Questions

Problem 4.98PAE

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