Question

A buffer solution is prepared by mixing 200cm3 of 2.00moldm–3 propanoic acid, CH3CH2COOH, with 600cm3 of 1.00moldm–3 sodium propanoate, CH3CH2COONa
Ka for CH3CH2COOH = 1.32 × 10–5moldm–3
What is the pH of the buffer solution?

Answer 1

Answer:

5.18

Explanation:

The other guys answer isn't an option and its a multiple choice question lol his equation is wrong

Answer 2

Concept:

A buffer is an aqueous solution made up of a weak acid and its salt (acid buffer) or a weak base and its salt (basic buffer). When a small quantity of strong acid or base is given to it, its pH changes very little, and it is therefore employed to keep the pH of a solution from changing.

Given:

The concentration of propanoic acid = 2.00 mol dm⁻³

The volume of propanoic acid = 200 cm³ = 200 ml

The concentration of sodium propanoate = 1.00 mol dm⁻³

The volume of sodium propanoate = 600 cm³ = 600 ml

Ka for CH₃CH₂COOH = 1.32 * 10⁻⁵

Find:

What is the pH of the buffer solution?

Solution:

The expression for the pH of the acidic buffer solution is as given below:

              pH = pKa + log $\frac{[Salt]}{[Acid]}$

By substituting the given values in the above expression we can calculate the concentration of salt and concentration of acid.

[Salt] = $\frac{600 * 1.00}{100}$ = 6 M

[Acid] = $\frac{200 * 2.00}{100}$ = 4 M

Substitute the values in the above equation.

pH = 1.32 * 10⁻⁵ + log $\frac{6}{4}$

pH = 1.32 * 10⁻⁵ + 0.17609

pH = 0.0000132 + 0.17609

pH = 0.1761032

pH = 0.18

Hence the pH of the buffer solution prepared is 0.18.

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