Questions: The Ka of benzoic acid is 6.46 x 10-5. Determine its buffer range

The Ka of benzoic acid is 6.46 x 10-5. Determine its buffer range

Solution

Solution Steps

Step 1: Understanding the Buffer Range Concept

The buffer range of a weak acid is typically within one pH unit above and below its pKa value. The pKa is the negative logarithm of the acid dissociation constant (\(K_a\)).

Step 2: Calculate the pKa of Benzoic Acid

To find the pKa, we use the formula: \[ \text{pKa} = -\log(K_a) \] Substituting the given \(K_a\) value: \[ \text{pKa} = -\log(6.46 \times 10^{-5}) \]

Step 3: Compute the pKa Value

Calculating the logarithm: \[ \text{pKa} \approx 4.1897 \]

Step 4: Determine the Buffer Range

The buffer range is approximately one pH unit above and below the pKa: \[ \text{Buffer Range} = (\text{pKa} - 1, \text{pKa} + 1) \] Substituting the pKa value: \[ \text{Buffer Range} = (4.1897 - 1, 4.1897 + 1) = (3.1897, 5.1897) \]

Final Answer

The buffer range of benzoic acid is \(\boxed{(3.1897, 5.1897)}\).

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