Neco 2018 Chemistry Question 7

Practice essay / theory question 7 from the 2018 Neco Chemistry examination. This question covers Acids, Bases and Salts .

Neco 2018 Chemistry Essay / Theory

Topic: Acids, Bases and Salts

Question 7 NECO • 2018 • CHEMISTRY • essay

A 0.250 mol dm\(^{-3}\) solution of the weak acid HA (\(K_{a}=1.2\times10^{-5}\)) is mixed with its sodium salt NaA to prepare 250 cm\(^{3}\) of a buffer solution. The solution is subsequently titrated with 0.100 mol dm\(^{-3}\) NaOH. Answer the following questions.

( a )

Calculate the pH of the buffer before any NaOH is added. (Assume the ratio [A\(^{-}\)]/[HA] = 1.5.)

( b )

After adding 10.0 cm\(^{3}\) of the NaOH solution, calculate the new pH of the buffer.

( c )

How many millilitres of the 0.100 mol dm\(^{-3}\) NaOH solution are required to raise the pH of the original buffer by 0.50 units?

( d )

Explain, with reference to the common‑ion effect, why the buffer resists large changes in pH when small amounts of strong acid or base are added.

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This is Neco 2018 Chemistry Question 7. It is one of the essay questions from the 2018 Neco Chemistry examination.

The question covers Acids, Bases and Salts .

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