DP Chemistry (last assessment 2024)

Question 19N.3.sl.TZ0.16d

Date	November 2019	Marks available	[Maximum mark: 1]	Reference code	19N.3.sl.TZ0.16d
Level	sl	Paper	3	Time zone	TZ0
Command term	Calculate	Question number	d	Adapted from	N/A

[Maximum mark: 1]

19N.3.sl.TZ0.16d

Body fluids have different pH values.

(d)

Calculate the pH of a buffer solution which contains 0.20 mol dm⁻³ ethanoic acid and 0.50 mol dm⁻³ sodium ethanoate. Use section 1 of the data booklet.

pK_a (ethanoic acid) = 4.76

[1]

Markscheme

«pK_a = 4.76»
«pH = pK_a + log $\left( {\frac{{\left[ {{\text{C}}{{\text{H}}_3}{\text{CO}}{{\text{O}}^ - }} \right]}}{{\left[ {{\text{C}}{{\text{H}}_3}{\text{COOH}}} \right]}}} \right)$ »
«pH = 4.76 + 0.40 =» 5.16 ✔

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Core

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Options » D: Medicinal chemistry » D.4 pH regulation of the stomach

Options » D: Medicinal chemistry

Core » Topic 8: Acids and bases » 8.3 The pH scale

Core » Topic 1: Stoichiometric relationships » 1.3 Reacting masses and volumes

Core » Topic 1: Stoichiometric relationships

Core » Topic 8: Acids and bases

Question 19N.3.sl.TZ0.16d

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