Question

A solution is made by mixing 0.82 grams of sodium acetate, 1 mL of 12 M acetic acid (pKa=4.76) and water to give a final volume of 1 L. ______________ evaluates the usefulness of this solution as a buffer.

Answer 1

Answer:

This solution acts as an efficient buffer

Explanation:

the pH of a buffer solution can be described like this: $pH=pKa+log\frac{[base]}{[acid]}$

[acid]=[acetic acid]=$1mL.\frac{12mol}{1000mL} . \frac{1}{1L} = 0.012M$

[base]=[sodium acetate]=$0.82g.\frac{1mol}{82g} .\frac{1}{1l} = 0.01M$

replacing, $pH=4.76+log\frac{0.01M}{0.012M} =4.84$

If we add an acid, pH will decrease a little bit and if we add a base, pH wil increase a little bit.

lets supose that we change the rate by increasing [base] to 0.1, then

$pH=4,76+log\frac{0.1}{0.012} = 5.68$

and now lets supose that we increase [acid] to 0.1 $pH=4.76+log\frac{0.01}{0.1} = 3.76$

Big changes in concentration of base or acid doesn´t produce big changes in pH, in that way the mix of sodium acetate with acetic acid is a good buffer solution.