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2 years ago

You have a 250. -ml sample of 1. 28 m acetic acid (ka = 1. 8 x´ 10–5). calculate the ph of the best buffer.

Chemistry

2 answers:

exis [7]2 years ago

7 0

The ideal buffer's pH value is 4.74..

What is best buffer ?

The Best Buffer is a buffer that has equal amounts of the weak acid and its conjugate base. It responds well to the addition of acids and bases in order to fend off pH changes. A mixture of the weak base and its conjugate acid, or the weak acid and its conjugate base, is referred to as a buffer solution.

Here weak acid is acetic acid CH3COOH

The following equation can be used to determine a buffer's pH:

pH = pka + logconjugate baseweak acid

Now, the weak acid and its conjugate base are present in equal amounts in the optimal buffer.

Therefore,

Conjugate base = weak acid

This implies that,

pH = pka + log 1

pH = pka + 0

pH = pka

Now, pka can be written as -log ka

The value of ka is given as 1.8 * 10-5

Therefore,

pH = -log (1.8 * 10-5)

pH = 4.74

As a result, the ideal buffer has a pH of 4.74..

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Nadya [2.5K]2 years ago

4 0

The ph of the best buffer is 4.74

The given acetic acid is a weak acid

The equation of the pH of the buffer

pH = pKa + log ( conjugate base / weak acid ).

For best buffer the concentration of the weak acid and its conjugate base is equal.

pH = pKa + log 1

pH = pKa + 0

pH = pKa

given Ka = 1.8 × 10⁻⁵

pKa = - log ka

pH = -log ( 1.8 × 10⁻⁵ )

pH = 4. 74

Hence the pH of the best buffer is 4.74

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