What's the significance and difference of pKa and pKb (chemistry)?

Question

There was an analysis report asked to me by my boss about the significance of the knowledge of pKb of our product. We produce cosmetics raw materials. He was somewhat expecting a practical answer from me. And I couldn't figure how it is important for us to know the value of pKb of our products. And I really can't get the importance. And why do our customers need to know it. Please could you explain me the significance and maybe the way how to figure out pKa and pKb value. And maybe explain to me in a very practical way its usage? Thanks...

Answer 1

The basicity constant or pKb is a measure of basicity and related to the pKa by the simple relationship pKa + pKb = 14.

The pKa (and thus the pKb) of many coumpounds can be found in appropriate table on-line (see the second site) or you can do a search for a specific compound by typing the name and adding "+pKa" into a search engine.

If your products are water soluble, you can make a dilute aqueous solution and measure the pH of the solution.

For cosmetics and skin care products a pH of 5.5 to 6.5 (mildly acid) is often best. Harsh soaps can have pH = 9.0 to 11.0 (very basic). A pH of 7.0 is often called "balanced".

Answer 2

Pka Meaning

Answer 3

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RE:
What's the significance and difference of pKa and pKb (chemistry)?
There was an analysis report asked to me by my boss about the significance of the knowledge of pKb of our product. We produce cosmetics raw materials. He was somewhat expecting a practical answer from me. And I couldn't figure how it is important for us to know the value of pKb of our products....

Answer 4

It basically tells you how much or to what extent that acid (or base) dissociates, or comes apart. For HCl and H2SO4, they dissociate 100%, so we don't use Ka for them. But for a weak acid like acetic acid, you don't get 100% dissociation. HAc ==> H+ + Ac-, and then chemists use the Ka (a fixed number, i.e. a constant for HAc) to calculate how much of each species is in solution. If you had 1 M HCl, you would have 1 M H+ and 1 M Cl-, but for HAc, this isn't the case. Hope this explains what dissociation constant means in simple english.

Answer 5

Smaller Pk value means Stronger.
So Smaller Pka value means Stronger (a)cidity
and, Smaller Pkb value means Stronger (b)acisity.

Answer 6

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pKa and pKb measure the extent to which the substance behaves as an acid or base. The smaller the value of pKx, the better it is at acting as that thing. For your first example, it is a better base than it is an acid. The second example, it is a better acid than a base.