Waec Model Questions Vol1 2017 Chemistry Question 7

Practice essay / theory question 7 from the 2017 Waec Model Questions Vol1 Chemistry examination. This question covers Acids, Bases, Buffers, Equilibrium constants, Temperature effect on equilibrium .

Waec Model Questions Vol1 2017 Chemistry Essay / Theory

Topics: Acids Bases Buffers Equilibrium constants Temperature effect on equilibrium

Question 7 WAEC_MODEL_QUESTIONS_VOL1 • 2017 • CHEMISTRY • essay

A weak monoprotic acid HA (Ka = 1.8 × 10⁻⁵) is dissolved in water to give a 0.200 mol solution in a 1.00 L flask. Afterwards 0.150 mol of its sodium salt NaA is added to the same solution.

Question Parts

( a )

Calculate the pH of the resulting solution at 25 °C.

( b )

A further 0.050 mol of NaOH is added to the mixture. Calculate the new pH and state whether the buffer now lies on the acidic or basic side of the pKa.

( c )

The dissociation of HA is endothermic with ΔH° = +12 kJ mol⁻¹. Discuss qualitatively how raising the temperature from 25 °C to 35 °C would affect the pH of the original buffer (before NaOH addition).

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About This Question

This is Waec Model Questions Vol1 2017 Chemistry Question 7. It is one of the essay questions from the 2017 Waec Model Questions Vol1 Chemistry examination.

The question covers Acids, Bases, Buffers, Equilibrium constants, Temperature effect on equilibrium .

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