DP Chemistry (last assessment 2024)

Question 19N.3.hl.TZ0.b(iii)

b(iii).

[Maximum mark: 1]

19N.3.hl.TZ0.b(iii)

Aspartame is formed from the two amino acids aspartic acid (Asp) and phenylalanine (Phe).

Chromatography is used in the analysis of proteins in the food and pharmaceutical industry.

Calculate the ratio of [A⁻] : [HA] in a buffer of pH 6.0 given that pK_a for the acid is 4.83, using section 1 of the data booklet.

[1]

Markscheme

«6.0 = 4.83 + log $\frac{{\left[ {{{\text{A}}^ - }} \right]}}{{\left[ {{\text{HA}}} \right]}}$ »

«log $\frac{{\left[ {{{\text{A}}^ - }} \right]}}{{\left[ {{\text{HA}}} \right]}}$ = 1.17»

«[A⁻] : [HA] =» 14.8 : 1 ✔

NOTE: Accept “15:1”.
Do not accept 1:14.8.

Syllabus sections