Engineering
Chemistry
Acid Base Titration and Curves
Question

When a weak base solution (50 mL of 0.1 M NH4OH) is titrated with a strong acid (0.1 M HCl), the pH of solution initially decreases fast and then decreases slowly till near equivalence point (as shown in the figure). Which of the following statements is/are true ?

 The initial fast decrement in pH is due to fast consumption of free OH ions by HCl.

The slow decrease of pH is due to formation of an acidic buffer solution after addition of some HCl.

The slope of shown pH graph  (magnitude only) will be minimum when 25 mL of 0.1 M HCl is added.

The slow decrease of pH is due to formation of a basic buffer solution after addition of some HCl.

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Solution

Initial decrement is due to consumption of free OH ions, then slow decrement in pH is due to basic buffer solution and minimum slope will be there when there is best buffer action ([salt] / [base] = 1)

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