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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Petey04 on November 20, 2006, 01:54:25 AM

Title: Calculating Kb and pKb of weak organic base?
Post by: Petey04 on November 20, 2006, 01:54:25 AM

I have tried this a few times but know I must be getting wrong answers.
C18H21NO3 is a weak organic base with 5.0x10^-3M and pH of 9.95
I need to calculate Kb and pKb.

Started with: Kb=[C18H20ON2+][OH-]/[C18H21NO3] which I'm not sure is correct.

Also, I might as well ask: In a 0.100 M neutral solution of salt, what is the identity of the salt?
These are what I've narrowed it down to: KBr, NH4Cl, KCN or K2CO3

Title: Re: Calculating Kb and pKb of weak organic base?
Post by: AWK on November 20, 2006, 02:48:15 AM

Quote

Started with: Kb=[C18H20ON2+][OH-]/[C18H21NO3] which I'm not sure is correct.

Good start.
Hint
[C18H20ON2+] is equal aproximately to [OH-]
and convert pH to pOH then to {OH-]

Quote

These are what I've narrowed it down to: KBr, NH4Cl, KCN or K2CO3

Only KBrfrom these above is neutral in water solution