Answer the following: -What is the relation between the pka of an acid and the s

Question

Answer the following:


-What is the relation between the pka of an acid and the strengthof the acid?

-Find the pka. For an acid HA, the concentration of HA and A- are0.075 and 0.025, respectively, at pH 6.0. What is the pkA value forHA?

-pH indicator. A dye that is an acid and that appears as differencecolors in its protonated and deprotonated forms can be used as a pHindicator. Suppose that you have a 0.001 M solution of a dye with apka of 7.2,. From the color, the concentration of the protonatedform is found to be 0.0002 M. Assume that the remainder of the dyeis in the deprotonated form. What is the pH of the solution?

-What's the ratio? An acide with a pka of 8.0 is present in asolution with a pH of 6.0. What is the ratio of the protonated tothe deprotonated form of the acid?

Explanation / Answer

protonated form = HIn (this is the acid form)

deprotonated form = In- (this is the base form, also called the salt form)

We will use the Henderson-Hasselbalch equation:

pH = pKa + log [salt] / [acid]

pH = 7.2 + log (0.00080 / 0.00020)

pH = 7.8

The concentration of the deprotonated (salt) form was found like this:

0.0010 M minus 0.00020 M = 0.00080 M

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