Waec Model Questions Vol1 2022 Chemistry Question 7

Practice essay / theory question 7 from the 2022 Waec Model Questions Vol1 Chemistry examination. This question covers Acids, Bases, Buffers, pH calculations, Temperature effect on Ka .

Waec Model Questions Vol1 2022 Chemistry Essay / Theory

Topics: Acids Bases Buffers pH calculations Temperature effect on Ka

Question 7 WAEC_MODEL_QUESTIONS_VOL1 • 2022 • CHEMISTRY • essay

A student prepares a buffer solution by dissolving 0.200 mol of acetic acid (CH₃COOH) and 0.150 mol of sodium acetate (CH₃COONa) in enough water to make 1.00 L of solution. The acid dissociation constant of acetic acid at 25 °C is Ka = 1.8 × 10⁻⁵. The student then adds 0.0050 mol of a strong acid (HCl) to the buffer and records the change in pH. Answer the following questions:

Question Parts

( a )

Calculate the initial pH of the buffer solution before any strong acid is added. Show all steps.

( b )

After the addition of 0.0050 mol HCl, calculate the new pH of the solution. State any assumptions made.

( c )

Explain qualitatively how an increase in temperature would affect the pH of this buffer solution. Relate your answer to the temperature dependence of Ka for acetic acid.

( d )

Using the data from parts (a) and (b), determine the buffer capacity (β) of the solution, defined as β = Δn / ΔpH, where Δn is the amount (in moles) of strong acid added.

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About This Question

This is Waec Model Questions Vol1 2022 Chemistry Question 7. It is one of the essay questions from the 2022 Waec Model Questions Vol1 Chemistry examination.

The question covers Acids, Bases, Buffers, pH calculations, Temperature effect on Ka .

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