definition of a buffer

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Sue Bin Park 2I
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definition of a buffer

Postby Sue Bin Park 2I » Mon Jan 20, 2020 5:45 pm

what exactly is the practical definition of a buffer? wouldn't any solution of a weak acid/base be a buffer because the acid/base and its conjugate would exist in solution? or am i getting this all confused lol

505306205
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Re: definition of a buffer

Postby 505306205 » Mon Jan 20, 2020 6:03 pm

A buffer is a solution that contains both conjugates. In the ICE table, therefore, the starting concentration for the conjugate acid/base is not 0.

Jordan Young 2J
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Re: definition of a buffer

Postby Jordan Young 2J » Mon Jan 20, 2020 6:22 pm

A buffer has a weak acid/base and its conjugate so that it can thus resist a chance in pH. You want to have large enough concentrations of both so that it can react if an acid or base is added to the solution

Joowon Seo 3A
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Re: definition of a buffer

Postby Joowon Seo 3A » Mon Jan 20, 2020 6:24 pm

A buffer has a weak acid/base with its conjugate. The conjugate can take/give a proton in solution, so it can resist a change in pH.

aishwarya_atmakuri
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Re: definition of a buffer

Postby aishwarya_atmakuri » Mon Jan 20, 2020 6:32 pm

A buffer is a solution that resists changes in pH and it’s made by mixing a weak acid/base with its conjugate.

Hussain Chharawalla 1G
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Re: definition of a buffer

Postby Hussain Chharawalla 1G » Mon Jan 20, 2020 6:36 pm

If you use a weak acid or weak base, wouldn't it's conjugate be a strong base/acid? So if the buffer demands equal concentrations of weak acid and base, how would it be created?

Sue Bin Park 2I
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Re: definition of a buffer

Postby Sue Bin Park 2I » Thu Jan 23, 2020 10:47 am

Hussain Chharawalla 1G wrote:If you use a weak acid or weak base, wouldn't it's conjugate be a strong base/acid? So if the buffer demands equal concentrations of weak acid and base, how would it be created?


i'm pretty sure the conjugate seesaw is only relative; if the acid is weakER then its conjugate base is strongER, etc. irl, if you have a weak acid with a conjugate base that is categorized as strong, it would actually mean the weak acid basically doesn't deprotonate. vice versa with a weak base and strong acid. HCl is a strong acid - its conjugate base Cl- ion doesn't protonate period.

it's like a spectrum
strong acid <--B---A----neutral H2O-B---A-----> strong base
a moderately weak acid/moderately weak conjugate base pairing (A and A) will fall equidistant left and right of the neutral H2O centerpoint. if a weak acid is strongER then the acid will be farther from the center and pull the conjugate base closer to the neutral center point, categorizing it as a weaker base (B and B). if an acid is so strong that it is a literal strong acid, that is it completely dissociates, then that means the conjugate base is pulled into the center point (practically) and is effectively neutral in solution/doesn't protonate more than just H2O would on its own.

this push and pull is a result of the fact that the Ka and Kb have to multiply into the Kw constant always.

Leila_4G
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Re: definition of a buffer

Postby Leila_4G » Thu Jan 23, 2020 7:52 pm

Also, I'm not sure about the presence of a salt when making a buffer. Can someone please explain that to me? Thanks!

Emil Velasco 1H
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Re: definition of a buffer

Postby Emil Velasco 1H » Fri Jan 24, 2020 9:41 pm

A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa. Its pH changes very little when a small amount of strong acid or base is added to it.


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