Topic: Calculating pH of a weak base given pKb (Read 2300 times)

Budge · « **on:** April 02, 2019, 08:51:36 PM »

Could anybody lend me a hand with this calculation:

Pyridine is a weak organic base with pKb = 8.75. Determine the pH of a 0.33 M aqueous solution of pyridine at 25.0 °C

When I have attempted this, I end up with a pH greater than 14. Any help would be much appreciated!

Borek · « **Reply #1 on:** April 03, 2019, 02:48:40 AM »

Hard to say what you did wrong not seeing your work,. Show how you got the wrong result and we will start from there.

Budge · « **Reply #2 on:** April 04, 2019, 12:47:22 AM »

My working out is attached. I tried to use an ICE table to find the concentration of hydroxide ions so I could use that to calculate pOH and hence pH.

Borek · « **Reply #3 on:** April 04, 2019, 02:56:01 AM »

What is the difference between Kb and pKb?

Budge · « **Reply #4 on:** April 04, 2019, 07:57:00 AM »

Oh true, I can see I've substituted pKb into the equation where I should've put in Kb, thanks!

I would just need to take the negative log of pKb to find Kb right?

Borek · « **Reply #5 on:** April 04, 2019, 09:54:32 AM »

Quote from: Budge on April 04, 2019, 07:57:00 AM

I would just need to take the negative log of pKb to find Kb right?

Nope. You need to brush up your math.

What is the definition of the logarithm?

Topic: Calculating pH of a weak base given pKb (Read 2300 times)

Budge

Calculating pH of a weak base given pKb

Borek

Re: Calculating pH of a weak base given pKb

Budge

Re: Calculating pH of a weak base given pKb

Borek

Re: Calculating pH of a weak base given pKb

Budge

Re: Calculating pH of a weak base given pKb

Borek

Re: Calculating pH of a weak base given pKb

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