What is the ratio of acetate ion to acetic acid (Ka = 1.76*10-5) in a solution containing these compounds at pH 4.38? Write your answer as a decimal and not as a fraction.

Question

Chemistry

Thalia Vega

24 October, 14:14

What is the ratio of acetate ion to acetic acid (Ka = 1.76*10-5) in a solution containing these compounds at pH 4.38? Write your answer as a decimal and not as a fraction.

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Answers (1)

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Giggles · Answer 1

0.43.

Explanation:

In order to solve this question we will need the an equation called Henderson-Hasselbalch Equation. The Henderson-Hasselbalch Equation can be represented by the reaction below;

pH = pKa + log ([ A^ - ] / [ HA]).

Where HA is the acetic acid and A^ - is the Acetate ion

We are given the pH value to be = 4.38 and the ka to be = 1.76*10^-5. So, we will use the value for the ka to find the pKa through the formula below.

pKa = - log ka.

Therefore, pKa = - log (1.76*10^-5).

pKa = 4.75 + log

So,

4.38 = 4.75 + log ([ A^-] / [HA]).

4.38 - 4.75 = log ([ A^ - ] / [ HA]).

([ A^ - ] / [ HA]) = 10^ - 0.37.

([ A^ - ] / [ HA]) = 0.42657951880159265.

([ A^ - ] / [ HA]) = 0.43.