A student is asked to prepare 250.0 mL of an acetate buffer for an enzyme assay. Available reagents are 0.200 mol L\(^{-1}\) ethanoic acid (CH\(_3\)COOH) and 0.200 mol L\(^{-1}\) sodium ethanoate (CH\(_3\)COONa). The student targets a buffer with pH 4.76 at 25\(^\circ\)C, using \(K_a(\text{CH}_3\text{COOH}) = 1.8 \times 10^{-5}\). After preparation, the student tests the buffer by adding small measured volumes of 0.100 mol L\(^{-1}\) HCl(aq) and 0.100 mol L\(^{-1}\) NaOH(aq), mixing thoroughly after each addition. Assume volumes are additive and that activity effects are negligible.
The student repeats the test by adding 5.00 mL of 0.100 mol L\(^{-1}\) NaOH(aq) to a fresh 250.0 mL portion of the original buffer (from part (a)). Calculate the new pH and compare, using your results, the buffer’s response to added acid versus added base.
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Create Free Account Log inThis is a free HSC HSC Chemistry practice question worth 5 marks, testing your understanding of Conduct a practical investigation to prepare. It falls under Quantitative Analysis in Module 6: Module 6: Acid/Base Reactions. Submit your answer above to receive instant AI-powered marking and personalised feedback.
Students analyse how and why the definitions of both an acid and a base have changed over time, and how the current definitions characterise the many chemical reactions of acids. Acids react in particular ways to a variety of substances. These reactions follow a pattern that students identify and explore in detail. Acids and bases, and their reactions, are used extensively in everyday life and in the human body. The chemistry of acids and bases contributes to industrial contexts and the environment. Therefore, it is essential that the degree of acidity in these situations is continually monitored. By investigating the qualitative and quantitative properties of acids and bases, students learn to appreciate the importance of factors such as pH and indicators.
Inquiry question: How are solutions of acids and bases analysed?
conduct a practical investigation to prepare a buffer and demonstrate its properties (ACSCH080)
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