Which of the following combinations would act as buffered solutions

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Discussion Overview

The discussion revolves around identifying which combinations of chemical substances would act as buffered solutions. Participants examine various pairs of acids and their corresponding bases, considering their strengths and properties in the context of buffer solutions.

Discussion Character

  • Homework-related, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant asserts that HCl is a strong acid, eliminating it as a candidate for a buffered solution.
  • Another participant argues that a buffer requires the presence of a weak acid and its conjugate base, suggesting that both b (CH_3COOH and KCH_3COO) and c (H_2S and NaHS) could work as buffers.
  • A participant expresses uncertainty about whether to choose one or both options in a multiple-choice format.
  • Another participant suggests that if only one answer is correct, one of the solutions may not be stable and could lose components quickly.
  • A question is raised about determining the speed of reactions based on chemical formulas, to which a participant responds that it is not about reaction speed but rather the properties of H2S.

Areas of Agreement / Disagreement

There is disagreement regarding the criteria for a buffered solution and the interpretation of the multiple-choice question. Some participants believe both b and c are valid, while others suggest only one may be correct based on stability concerns.

Contextual Notes

Participants reference the need for weak acids and their conjugate bases in buffer solutions, but there is ambiguity regarding the definitions and properties of the substances involved, as well as the implications of stability in a multiple-choice context.

Who May Find This Useful

Students studying chemistry, particularly those focusing on acid-base equilibria and buffer solutions, may find this discussion relevant.

JessicaHelena
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Homework Statement



Which of the following combinations would act as buffered solutions?
a. HCl and NaCl
b. CH_3COOH and KCH_3COO
c. H_2S and NaHS
d. H_2S and Na_2S

Homework Equations



none really... The acid needs to be weak and the base strong though.

The Attempt at a Solution



HCl is one of the strongest acid, so that eliminates a. Since the conjugate base of H_2S should be HS^-, that also eliminates d., which has somehow gotten rid of the other H as well. However, I'm having a difficulty choosing between b and c because CH_3COOH and H_2S are both weak acids (from what I've learnt), which makes them good candidates for a buffered solution.
 
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JessicaHelena said:
The acid needs to be weak and the base strong

No, that's not how it works. Buffer needs presence of an acid and its conjugate base - neither should be really strong. Plus, pKa + pKb = pKw, so their strengths are not independent.

Somehow you managed to get close to the correct answer though - both b and c will work as buffers.
 
Oh okay. However, since this is a multiple choice question, I think I’m supposed to choose only one of them...
 
If it is a multiple choice you can as well select two.

If you were told there is only one correct answer one of these solutions won't be stable and will be loosing (quite fast) one of its components.
 
Is there any way I can tell the speed of the reactions by looking at the chemical formulas?
 
No, but it is not about speed of the reaction. What do you know about properties of H2S?
 

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