Igcse Model Questions Vol1 2018 Chemistry Question 7

Practice essay / theory question 7 from the 2018 Igcse Model Questions Vol1 Chemistry examination. This question covers Acids, Bases, Salts, Buffer solutions .

Igcse Model Questions Vol1 2018 Chemistry Essay / Theory

Topics: Acids Bases Salts Buffer solutions

Question 7 IGCSE_MODEL_QUESTIONS_VOL1 • 2018 • CHEMISTRY • essay

A student prepares a buffer solution using acetic acid (CH₃COOH) and its conjugate base sodium acetate (CH₃COONa). She dissolves 0.20 mol of acetic acid in 500 mL of water and then adds solid sodium acetate until the pH of the solution is 5.00 at 25 °C. The acid dissociation constant of acetic acid is Ka = 1.8 × 10⁻⁵.

Question Parts

( a )

Write the acid‑dissociation equilibrium equation for acetic acid and define the meaning of Ka.

( b )

Using the Henderson–Hasselbalch equation, calculate the number of moles of sodium acetate that must be added to obtain a pH of 5.00. Show all steps and state any assumptions made.

( c )

Explain why the resulting solution functions effectively as a buffer. In your answer, describe the role of the conjugate base and the effect of adding a small amount of a strong acid or a strong base.

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About This Question

This is Igcse Model Questions Vol1 2018 Chemistry Question 7. It is one of the essay questions from the 2018 Igcse Model Questions Vol1 Chemistry examination.

The question covers Acids, Bases, Salts, Buffer solutions .

View More Igcse Model Questions Vol1 2018 Chemistry Questions More Igcse Model Questions Vol1 Practice Questions Back to Questions

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