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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: blazingwes on April 14, 2006, 12:23:26 PM

Title: help on buffer question
Post by: blazingwes on April 14, 2006, 12:23:26 PM
i need help on one of my questions on my hw assignment.. i don't know how to do it.

how you one make a one liter solution with a pH os 5.00, so that it will be buffered?  (Use a 0.100 M acid solution)

wath is the pH of the solution if acid is added so that the Hydrogen ion concentration is .100M
Title: Re: help on buffer question
Post by: Borek on April 14, 2006, 01:37:17 PM
What acid? Do you know what Henderson-Hasselbalch equation (http://www.chembuddy.com/?left=pH-calculation&right=pH-buffers-henderson-hasselbalch) is?
Title: Re: help on buffer question
Post by: blazingwes on April 14, 2006, 01:55:44 PM
soo will this be the correct answer?
adding .100 M of nitrous acid to 4.47 M of nitrite to get a buffer of ph 5.00..

but.. i don't understand the 2nd question
Title: Re: help on buffer question
Post by: Borek on April 14, 2006, 02:11:06 PM
For pH 5.0 acetic acid will be much beter. Nitrous acid has pKa = 3.37, with pH 5.0 you are too far from the pKa for buffer to be effective, see plot at buffer capacity (http://www.chembuddy.com/?left=pH-calculation&right=pH-buffer-capacity) lecture.

Looks like the second question has nothing to do with buffers :)
Title: Re: help on buffer question
Post by: blazingwes on April 14, 2006, 02:54:25 PM
one more question wat is a singel-step equation????


how you write BaSO3 +H+ = Ba2+ + H2SO4
Title: Re: help on buffer question
Post by: Alberto_Kravina on April 14, 2006, 02:57:37 PM
Quote
how you write BaSO3 +H+ = Ba2+ + H2SO4

Err....I think that something is wrong! It should be BaSO4 + H+ ----> Ba2+ + H2SO4

Well, try to solve it by yourself, it's pretty easy....
Title: Re: help on buffer question
Post by: AWK on April 15, 2006, 06:39:28 AM

Err....I think that something is wrong! It should be BaSO4 + H+ ----> Ba2+ + H2SO4

Well, try to solve it by yourself, it's pretty easy....
Quote
But wit nitric acid this reaction is possble!
BaSO3 + H(+) + NO3(-) = Ba2+ + SO4(2-) +NO +H2O (unbalanced !)
Title: Re: help on buffer question
Post by: Alberto_Kravina on April 15, 2006, 07:15:27 AM
I know that the sulfite anion can be oxidated to Sulfate, however, I thought that the reaction that blazingwes meant was just the protonation of the sulfite anion with a (strong) acid.... :(
Title: Re: help on buffer question
Post by: Borek on April 15, 2006, 08:35:48 AM
I am afraid even blazingwes is not 100% sure what s/he is asking about :(