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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: helpme89 on March 14, 2008, 11:37:26 PM

Title: Buffer solutions volume ratio
Post by: helpme89 on March 14, 2008, 11:37:26 PM

so i have a question that is puzzling me so much i can not figure it out mabey you guys can guide me through it !
In what volume ratio should you mix 1.0 solutions of  NH4Cl and NH3 to produce a buffer solution having a pH = 9.70?

thank you

Title: Re: Buffer solutions volume ratio
Post by: Borek on March 15, 2008, 05:00:15 AM

Google Henderson-Hasselbalch equation.

Title: Re: Buffer solutions volume ratio
Post by: helpme89 on March 15, 2008, 07:29:01 PM

I ahve tried googling and calling other chemistry students buh no luck .. if someone could help me that would be very much appreciated!

Title: Re: Buffer solutions volume ratio
Post by: Borek on March 15, 2008, 07:32:33 PM

Google and write Henderson-Hasselbalch equation.

Title: Re: Buffer solutions volume ratio
Post by: Arkcon on March 15, 2008, 07:44:48 PM

There is no way to solve this problem without using the Henderson-Hasselbalch equation.  I'm sure that very name is in the index of your text book, we need it to even start to figure out how to use the info you've been given.

Title: Re: Buffer solutions volume ratio
Post by: helpme89 on March 16, 2008, 10:34:35 PM

sorry i misunderstood what you guys were trying to sya yes you need Henderson equation but i just do not know how to apply it to this question here it is :

 
pH = PKa + log (Base/ Acid)

much appreciation again!
 

Title: Re: Buffer solutions volume ratio
Post by: enahs on March 16, 2008, 10:42:03 PM

So. You know the pH you want. You know your acids and bases. Look up the pKa. Solve for the ratio in the log term. Walk away.

Title: Re: Buffer solutions volume ratio
Post by: Arkcon on March 17, 2008, 06:54:24 AM

Good, now, which of your reagents is the acid, and which is the base?