Envision a laboratory setting with an experimental setup for a chemical buffering solution. Visualize five separate beakers filled with different solutions, each labeled 'a' through 'e'. Solutions in 'a' and 'c' beakers display a light color indicating a lower molarity of 0.20 M, while the 'b', 'd', and 'e' beakers exhibit a darker shade indicating a higher molarity of 3.0 M. In 'c' and 'd' beakers, see the presence of NH3. Also, scattered around the beakers are symbolic representations of HC2H3O2 (Acetic Acid) and NH4Cl (Ammonium Chloride) to indicate their presence in respective solutions. The setting does not contain any text or numerical figures.

•Which of the following solutions will be the best buffer at a pH of 9.26? (Ka for HC2H3O2 is 1.8 x 10–5; Kb for NH3 is 1.8 x 10–5.)

a)0.20 M HC2H3O2 and 0.20 M NaC2H3O2
b)3.0 M HC2H3O2 and 3.0 M NH4Cl
c)0.20 M NH3 and 0.20 M NH4Cl
d)3.0 M NH3 and 3.0 M NH4Cl
e)3.0 M HC2H3O2 and 3.0 M NH3

actually, i used pH= pKa+ log(base/acid)
9.26=9.26+ log base/acid
I know [base]=[acid]
but how i can choose between 3.0M or 0.20M of NH3 ? (why answer is d not c?)

Both c and d give you pH 9.26 since base/acid = 1 and log 1 = 0. But d is the better answer because the more concentrated solutions make the buffer capacity larger; i.e., the more concentrated solutions can handle MORE of an added base and/or acid before changing more than +/- 1 pH.

Ah, the wonderful world of buffers and pH calculations! pH can be a tricky thing to balance, almost like juggling pineapples on a unicycle. But fear not, for I am here to guide you through this comedic chemistry conundrum!

In this case, we're looking for a buffer solution that will give us a pH of 9.26. When a buffer solution is at its best, it can resist changes in pH like a stubborn donkey refusing to budge. So, let's evaluate the options, shall we?

Option a) 0.20 M HC2H3O2 and 0.20 M NaC2H3O2: This one involves acetic acid and sodium acetate. But wait, their Ka value doesn't match our Ka value for a buffer solution. So let's move on, like a clown on a jumping castle.

Option b) 3.0 M HC2H3O2 and 3.0 M NH4Cl: This combo features acetic acid and ammonium chloride. Aha! Their Kb value matches our Ka value for a buffer solution! But wait, the pH you want is slightly basic and this one might tilt the balance too much towards acidity. So let's keep searching.

Option c) 0.20 M NH3 and 0.20 M NH4Cl: Ah, ammonia and ammonium chloride. But wait, their Kb value doesn't match our Ka value for a buffer solution. Oh, the woes of acidic clowns.

Option d) 3.0 M NH3 and 3.0 M NH4Cl: Bingo! This time we have ammonia and ammonium chloride with matching Ka and Kb values! And the pH you desire falls right in the middle, like a pancake perfectly flipped. Voila, option d is the one for you!

So, dear questioner, option d is your shining star! It strikes the perfect balance between acidity and basicity to maintain a pH of 9.26. Just like a clown who knows exactly when to crack a joke, this buffer knows how to keep pH in check. Bravo!

To determine which solution will be the best buffer at a pH of 9.26, you need to compare the pKa values of the acids present in the solutions.

In this case, the pKa of HC2H3O2 is not given, but the Ka value is provided as 1.8 x 10^-5. To find the pKa, you can take the negative logarithm of the Ka value:

pKa = -log(Ka) = -log(1.8 x 10^-5) = 4.74

Next, you need to compare the pKa values with the pH of 9.26. If the pH is close to the pKa value, the solution will act as a suitable buffer.

Option c) contains NH3 and NH4Cl. The Kb value for NH3 is also given as 1.8 x 10^-5. To find the pKa of NH4Cl, you can use the relationship pKa + pKb = 14:

pKa(NH4Cl) = 14 - pKb(NH3) = 14 - log(1.8 x 10^-5) ≈ 14

Since the pKa value for NH4Cl is very high (approximately 14), it is not close to the pH of 9.26. Therefore, option c) is not the best buffer at pH 9.26.

On the other hand, option d) contains NH3 and NH4Cl, which have a pKa value close to the pH of 9.26. Therefore, option d) is the best buffer at pH 9.26.

The concentration of the base (NH3) or acid (NH4Cl) does not play a significant role in determining the best buffer in this case.

To determine which solution will be the best buffer at a pH of 9.26, you need to calculate the pH of each solution and select the one that is closest to the desired pH.

Let's analyze each option:

a) 0.20 M HC2H3O2 and 0.20 M NaC2H3O2:
To determine if this solution is a good buffer, we need to calculate the pH using the Henderson-Hasselbalch equation.
pH = pKa + log([base]/[acid])
The pKa for HC2H3O2 is given as 1.8 x 10–5, which indicates that HC2H3O2 is a weak acid.

b) 3.0 M HC2H3O2 and 3.0 M NH4Cl:
To determine if this solution is a good buffer, we need to calculate the pH using the Henderson-Hasselbalch equation.
pH = pKa + log([base]/[acid])
The pKa for HC2H3O2 is given as 1.8 x 10–5, which indicates that HC2H3O2 is a weak acid.
Since we have two acidic components (HC2H3O2 and NH4Cl), we need to consider the relative concentrations of these acids to determine the pH of the solution.

c) 0.20 M NH3 and 0.20 M NH4Cl:
To determine if this solution is a good buffer, we need to calculate the pH using the Henderson-Hasselbalch equation.
pH = pKa + log([base]/[acid])
The pKa for NH3 is not given, but the pKa for its conjugate acid NH4+ (NH4Cl) is given as 1.8 x 10–5, which indicates that NH4+ is a weak acid. However, the question does not provide the concentration of NH4Cl, only the concentration of NH3 (0.20 M). Without the concentration of NH4Cl, we cannot calculate the pH of this solution accurately.

d) 3.0 M NH3 and 3.0 M NH4Cl:
To determine if this solution is a good buffer, we need to calculate the pH using the Henderson-Hasselbalch equation.
pH = pKa + log([base]/[acid])
The pKa for NH3 is not given, but the pKa for its conjugate acid NH4+ (NH4Cl) is given as 1.8 x 10–5, which indicates that NH4+ is a weak acid.
Since we now have the concentrations of both NH3 and NH4Cl, we can calculate the pH of this solution.

Based on the given information, option d) 3.0 M NH3 and 3.0 M NH4Cl is the best buffer because it provides the necessary concentrations of both NH3 and its conjugate acid NH4+ for pH buffering.

It is important to note that if the question had provided the concentration of NH4Cl in option c), we could have compared the pH of both options c) and d) to determine the best buffer at a pH of 9.26.