Three drops of a 1.0 mol dm -3 solution of HCl was added to 20 cm 3 of a solution of pH6.4. The pH of the resulting solution will be

Correct Answer is : less than 6.4

Correct Answer is : less than 6.4

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JAMB Chemistry 2013 Paper

Question : 13

Total: 44

Solution:

Concept:

Adding a strong acid increases the concentration of

\mathrm{H^+}

ions, lowering the pH.

Explanation:

The solution has pH

6.4

, so it is acidic and not buffered.

HCl is a strong acid, and it dissociates completely as

\mathrm{HCl \to H^+ + Cl^-}

Adding three drops of HCl solution introduces more

\mathrm{H^+}

ions into the

20\ \mathrm{cm^3}

solution.

Therefore, the concentration of

\mathrm{H^+}

increases, and the pH decreases.

So the resulting pH will be less than

6.4

Answer:

B. less than 6.4

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