# Which of the following combinations would act as buffered solutions

• JessicaHelena
In summary, buffered solutions require the presence of a weak acid and its conjugate base. HCl and NaCl, as well as H2S and Na2S, do not fit this criteria. CH3COOH and KCH3COO and H2S and NaHS are both possible combinations for buffered solutions, but only one should be chosen for a multiple choice question. The correct answer should be stable and not lose any of its components quickly. Additionally, the properties of H2S should also be considered when making a decision.
JessicaHelena

## 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.

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?

## What is a buffered solution?

A buffered solution is a solution that resists changes in pH when small amounts of acid or base are added. It contains a weak acid and its conjugate base, or a weak base and its conjugate acid.

## Why are buffered solutions important in science?

Buffered solutions are important in science because they help maintain a stable pH, which is crucial for many biological processes. They also allow for more accurate and precise experimental results.

## How do you know if a solution is buffered?

A solution is buffered if it contains both a weak acid and its conjugate base, or a weak base and its conjugate acid, in similar concentrations.

## What is the purpose of combining a weak acid and its conjugate base in a buffered solution?

The purpose of combining a weak acid and its conjugate base in a buffered solution is to resist changes in pH when small amounts of acid or base are added. The weak acid and its conjugate base act as a buffer, absorbing any added H+ or OH- ions to maintain a stable pH.

## Can any combination of weak acid and its conjugate base act as a buffered solution?

No, not every combination of a weak acid and its conjugate base will act as a buffered solution. The concentrations of the acid and its conjugate base must be similar, and the pKa of the acid must be close to the desired pH of the solution.

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