## pKa and pKb

Megan Cao 1I
Posts: 103
Joined: Sat Sep 07, 2019 12:18 am

### pKa and pKb

For pKa the greater the value the smaller the Ka value, and the weaker the acid. I understand how the smaller Ka value shows how it's a weak acid, however I can't understand how a greater pKa means a smaller Ka. Could someone possibly explain this?

jisulee1C
Posts: 149
Joined: Thu Jul 25, 2019 12:17 am

### Re: pKa and pKb

A greater pKa results in a smaller Ka because pKa = -log Ka. If you plug in values you can see that a stronger acid will have a larger Ka and thus a smaller pKa.

Bryan Chen 1H
Posts: 58
Joined: Mon Jun 17, 2019 7:24 am

### Re: pKa and pKb

it just happens to be this way because of the math. its similar to how a higher pH is less H+ concentration, just like how higher pKa is weaker acid

VioletKo3F
Posts: 103
Joined: Sat Sep 07, 2019 12:18 am

### Re: pKa and pKb

The equation is pKa = -log Ka. Due to the math, a larger Ka will mean a smaller pKa.

WGaines_2E
Posts: 47
Joined: Mon Nov 18, 2019 12:18 am

### Re: pKa and pKb

so mathematically if you say pKa = 1x10^-7, Ka will be 7, and vice versa. To find pKa from Ka you do 10^-(Ka)=10^-7. Say Ka is now 3. Then pKa becomes 1x10^-3. I hope you can see here that a larger Ka leads to a smaller pKa.